I have an 89 Iroc L98 with 60K miles on it. The car is stored winters so things kind of sit for awhile. If the car is hot or cold the car will shake and twitch like its missing or has a vac leak ever since I got the thing. It twicthes more often when the car gets heated up and it goes into hot idle rpm. It isnt real bad but noticible and is non detectable at any other rpm. The engine is strong. It has brand new plugs, wires, cap and rotor and it is well maintained. I looked for vac leaks but found none with the carb cleaner trick. I readjust the IAC valve perinstruction on this site with no change. It has Slp headers, no cat, ported plenum, screenless MAF, nonmoded ARAP prom, Hooker catback, and new MSD coil. It shook like this before the mods though. I was thinking that it may be that the injectors are becomming clogged slightly and causing this at idle. Any help is apperciated!!!!!

my $0.02 says EGR or vacuum leak

if the problem goes away when you rev up the engine it's probably EGR

check your codes for a Code 32 (EGR)

if you don't know how to do that you can view my instructions on my website: http://www.iroc-z.org/tech/troublecodes

good luck
colin

There are no codes being thrown by the computer at all and the egr valve is not stuck because I am able to move it up with my fingers from underneath the housing.

true, but did you test it with a vacuum gauge?

there are two kinds of EGRs, i'm not sure which ones 3rdgens got but some can be tested with a vacuum gauge..

you must have had your plenum off then if you were able to get at your EGR?

I dunno, i still think EGR but it could be something else like injectors or bad 02 sensor or something.. how many miles are on your O2 sensor? they should be changed atleast every 50,000 miles

O2 sensor was just replaces 500miles ago I will look into the egr valve...

If you think you have a vacuum leak, hook a vacuum gauge up to a vacuum source on the manifold when the engine is warmed up and at idle. It should read 20 in....