Car is a 95 SSEI.
Problem while at cruising speed, let'* say 40 mph, it runs as if I'm releasing the throttle and reapplying it to the same rpm. In other words it'* jurking or chugging and it'* steady as long as I have it at cruising speed. The more I apply throttle the less the problem. If I apply up to 1/2 throttle or more it goes away.

What I have done to the engine just before this happened.

Changed */C coupler
Replaced plugs, TR55
Changed engine oil & Filter
Replaced UIM and LIM gaskets
Replaced air filter.
GM O2 sensor
Throttle Positioning Sensor.
All Vacuum lines replaced

It'* showing a code which is to replace the IAT sensor which I have on order.

Any suggestions?

i see that the plugs were changed......what about the wires??

You did plug wires too right?

(I'm gonna kick you in the nuts for ordering an IAT) J/k buddy.

It ran good when I brought it home after purchasing the car, so I didn't replace the wires.

Bill........pm sent.

i had similar problems with my honda, found out the ignition timing was off..

Wonderboy.. our timing is controlled by the ECM/PCM and can not be set by means other than reprogramming.

Im thinking the plug wires might be a good place to start.

First check them to make sure they arent contacting anything that might cause a problem, like the O2 sensor wiring or the like.

I was in a similar situation after replacing the UIM on my old car, we changed the plugs but not the wires and it started having similiar symptoms, replaced the wires and they went away.

Good point LH..

Double check to make sure one isn't resting on the O2 wiring.

Actually I did change the O2 sensor, so I'm going to edit my first post and add it to the list. Oh Ya I remembered one more thing to add to the list.

Psst. F.. you can't get a sensor to position the throttle body.. only the throttle itself.

Did you look for a wire touching the O2?