well i figure if any place to post, i'll post here...and i've already done a long extensive search for similar problems to mine but nothing is close, especially when i keep reading post after post of modifications to their vehicles..

i own a pretty much stock 89 GTA Trans Am, 51,000 orginal miles.
350 TPI L98 engine. i bought this car about 3 months ago, in the process this car was already running rough, i decided since the car had a lil over 50k miles on it, i decided to have the heads done with new valve seals, guides, etc, i also had 4 of the injectors sent out to cruzin performance for cleaning and bought 4 new ones (standard), plus i bought a few modification like porting the plenum, tb airfoil, etc.. just little things nothing major...
plus i replaced the original EGR valve, part of that preventive maintence ordeal... The car was running great since i fixed it up and it now has 56,000 miles, no problems until....

last wensday afternoon picking up lunch from work my car started surging while i was crusin' like around 50mphs...then i realized my check engine light kicked on...when i got to the restaurant my car wouldn't idle at all...the tach was moving up and down and i could smell how rich the car was running and knew that something is wrong right off the bat...in order to keep the car from surging i had to tap the gas to keep it stable around a grand (rpm wise)
after work, i was looking up using our scan tool, found out the 02 sensor has thrown a code 45, which is Exhaust system rich...
sure enough i took just two plugs out and found that they are totally carbonated with fuel..not wet, wet...but enough to realize that the car is indeed running rich...
looking at the data i found that the car's blm (block learn memory is way below where it should be, running around 110 where as in normal conditions it's suppose to be running around 128)
and i even noticed the block learn intergrator was at 80! and i felt like something is indeed causing this to run this way...other info i found was that the pulse width on my car was totally long ...telling my injectors to go 6.9-7.0 milliseconds...that's alot of time keeping those injectors open! and that's not a good thing!
reading thru my mitchell on demand data...
i check for the obvious: or from what it told me to look for..
-check for leaking diaphram in the fuel pressure regulator....no leaks were detected...
-check for leaking injectors, sorry they're brand new plus the cleaned ones: i check them and they held pressure while the car was running and when it was off....running was like 45psi steadily, holding with koeo, it was hold around 45psi...so i know the injectors aren't leaking, and it's not a fuel delievery problem....but something else trying to make it run this way...
as i said before i already replace the EGR valve when i the heads was fixed...
and i've already tested it and it was good...and when i was testing it while the car was running, it kept closing down and wouldn't hold a vacuum which i believe it's good because the vacuum from the engine is forcing the egr to close...
-noticing the o2 sensor signal it is indeed reading it and fluxuating i feel safe to say that the o2 sensor is doing it's job telling the computer what it sees...
although it is staying over .5 volts and running rich as i can tell.
i've checked practically all the vacuum lines...and i couldn't find anything major rips tears, or broken lines...i mean seriously to make this car run this rich, it has to be a major vacuum leak if it is just that. ....
i've even put a vacuum gauge on and saw that it's running around 12 hg pounds but it's inconsistant, i know normally it should be running around 17hg, but if the car is running an eratic idle and fluxuates then it's hard to get a precise reading out of it, and if the car was running normal it would be a consistant idle like around 800rpms and therefore would read around 17hg because the car is making that vacuum...
although when i goosed the throttle the hg goes up for a brief second...so that show that somehow the vacuum is running somewhat proper...

at some point on mitchell on demand, it told me to test 02 sensor wire, and ground it...if you don't see the voltage of the o2 wire sensor go below .35 volts replace the ecm...well i did that and no it didn't go down past it, but it stayed at .39...i dunno if that would make a total difference...but i decided to replace the ecm ...i had to reuse the prom chip from the old ecm since the new one didn't come with one....and this new ecm is a aftermarket product from "Standard" which i strongly dislike ,but for now i didn't have a choice let alone was really surprised that my local parts store had something this in stock for a 13 y.o. vehicle...when i took out the one ECM out of the car it was already a remanufacture ECM by Delco Electronics, and so this isn't the orignal ECM!

well i took out all the spark plugs and yeah every one of them were carbonated heavenly, so i sand blasted them, and cleaned them...put them back in the engine, and after i reconnect all the wires to their proper location...i fired up the engine...and the car started up....at first it started up with an erratic idle, so i decided to do a idle relearn procedure...which it did smoothen out the rough idle some...
once again while running the car this time warm enough to reach close loop,
i was monotering the scanner and hooked up a vacuum gauge again, this time the vacuum was around 15-16 HG...higher then before, and yeah the idle was a bit more steady and higher...i even noticed the rich condition is gone because i couldn't smell it anymore,
plus the scanner was telling me that the block learn intergator is reading 128 but the BLM was reading 121, the injector pulse width was around 1.6-2.0 now, which is much more lower then it was before at idle!...the o2 was fluxuating very well when it hit closed loop, IAC was around 27-30 (fluxuating)..
i even went further to test the exhaust stream using our shop's 5 gas analyser...even though we don't have a dyno we perform a static idle and a 1500 rpm runs....
at idle here what i got:
02 was reading around 3.0% (lower the better)
C02 reading was around 13.2% (this is a good thing)
NOx was reading 22ppm (that's a very low number)
HC was reading 6ppm! very impressive..
now at 1500rpms in park:
02 was reading around 3.9%
CO2 was around 12.4%
NOx was reading around 58ppm
HC was around 11ppm
which what looks to be good all the way around..

however on my test drive: the car was a bogger, it lack the power it use to have...wouldn't acclerate well, and took awhile to get up to speed, the exhaust note sound a big more ruff, and while in drive at a stop, the car just shook, but not badly...

a couple more test i peformed before i left the shop today, i checked the timing using the EST bypass, and it was around 5-6 degrees where it should be... and it's suppose to be at 6 degrees
so it doesn't seem to be a timing problem at all either...
then i also used our infered heat gun onto the cats (my car has 2 cats: N10 code)....and going into the cats the heat was around 390 or so, going out the cats were around 410-415 degrees which doesn't seem to be a problem there!? so i don't get the deal here!....technically it seems the car is doing already, but when i drive it..it doesn't seem to be running right at all!?

my only conclusion so far to this is that there's something like a false sensor or something else causing it to run this way...
well i'm gonna do a search, hoping i could find something...and if anybody understood the tech info i posted here please reply of any ideas or help....i would totally appreciated...
all this time i was ready to go to the morris car show, has now gone to ashes...right now...i'll probably still go tommarow but damn why did it have to be this weekend? it's suppose to be nice tommarow....ugh...murphy's law "what ever can happen, will happen".....damn you murphy...