Sorry for the long post, but bare with me, im still new to this. my car is a 350 with 3.27 gears and using the "seat of the pants" test to see if my car is running right, i have come to the conclusion that im lacking a bit of low end power. I Have researched a lot and talked to a bunch of people, and they say that my car should be able to be able to burn the hell out of my tires from a stop. Prior to this weekend i would floor it from a stop and not even get a "squeek" from the tires. So i went out and got new AC Delco plugs (gapped to .035") new wires, cap, rotor and checked the timing (with that est plug unplugged) and its right at 6*btdc. (just making sure, its set 2 v's back from the big v. thats 6*'s right?) So after all that i took it for a 45min test drive, and it ran much better and it did spin the tires quite a bit, but not the way i think it should. Anyway, was about to put it in the garage and i got a code 34 and 42 to set. Proir to this, the CEL was not on. On a side note, only in turns, my car doesnt seem to shift down, i have to step on the gas a little to make it shift down. can that be whats making me think that i have a lack of low end power? if it is though, why do i have the code? What do you guys think? what should i check next? Knock sensor?

The 3.27 rear end is positive traction with 16" rims. If it has decent tires it is not going to "burn" the tires taking off in a straight line without power braking it. It should be turning a decent 1/4 mile time though. The people that "burn" their tires taking off usually have a "one wheel peel" rear end and 15" tires. And they get beat like a step-child in a race.
Make a 1/8 mile run and clock it.
Unhook the battery for 30 seconds and let the ECM relearn the engine with the new plugs and see if the codes still set.

if youre having trouble shifting, the tv cable might need an adjusting. are you running tpi?

Almost positive the TV cable is adjusted correct, it took me a while to get it right, but now it shifts well.

Yep, im running TPI

I had this 'exact' problem, try this:
Fill up with 93 octane and unplug the knock-sensor. I was getting timing retard really bad. This car used to be a 305 car and my guess is that the ESC or knock-sensor is still from the 305 car. My car runs "really" fast now.
The main thing I noticed is the downshift problem that you stated.
I also went from 14 mpg to 19 mpg (ALL highway miles)
I get no SES light with the knock-sensor unplugged, and no "audible" pre-ignition. But; now I have a REALLY fantastic/very responsive car.
Night-and-day difference. Now; this payday, I will replace the ESC and knock sensor with the 350 version. Im almost sure that I put a 350 knock-sensor (cant really remember,,,its been a long time) but NOT the 350 ESC module.
Is there a way to tell the 305 from the 350 knock sensor???
Good luck.
Funny thing is; I used to have a hi po 406 in this car with the same ESC and knock-sensor that is in there now, and I "DID NOT" have this problem.
It was really fast and responsive. I guess the 305 stuff will work with the 400; but, NOT with the 350???? Strange...

its 350, cool. lack of power? hmm most say thats typically, is the engine orginal or upgraded.

Ok. a bit of an update. I have gone through and replaced the plugs, wires, cap, rotor, and checked the timing. Some of the power was restored, but not to what i thought it should be. I also re-set the TV cable and the shifting problems is fixed.

The engine is the 350 tpi, orig.

Im going to be pulling the motor and trans next spring, to replace all the seals, and the flex plate which is cracked. I plan on replacing all the sensors at that time.

I always run 93 in the car, but as far as unplugging the knock sensor, wouldn't i get a SES light on all the time? Maybe ill give it a try anyway.

No SES light here; at least not from the KnockSensor.
I still get a 32 code ,,,egr is removed.
But not for long, I have an eprom programmer on the way
Try it, it wont hurt anything; AND it is a simple test.