Idle goes up and down.
 

You've all heard this before, and i've tried everything. Lets start. i have a 87 gxl. freshly rebuilt motor... k&N intake, TPS set, idle set, timing set. Yet the idle still bounces unless its set to 1200RPM or higher WTF@&$%!&#*%*(&. This has been happening before and after the rebuild. (new apex seals)... Tried the carb cleaner, helped very little... adjusting the tps seemed to have helped alot Any suggestions?

Oh yeah, i'm not sure if this is related, but sometimes if the clutch is released too quickly, the car sort of shakes violently as though the gas is pressed/released/pressed/released quickly and repeatedly.... perhaps this is related
anyways, thanks!!!

have you looked at the BAC valve lately?

I would suspect vac leak somewhere. I'm a 3rd gen driver and I had that due to a intake manifold gasket leak.

What's the bac valve and how do i check it? Well the vacuum leak is a valid explanation, however, since it was rebuilt, i'm sure he would have attached/inspected the hoses properly, as this happened before and after the rebuild.
*shrug*

I have the same problem right now. Im pretty sure that the shuddering of the car is directly related to the idle, since the revs are rising,dropping,rising, dropping, that would make it shake. It all started on mine after I had the intake off to port it, so Im ripping it back off this weekend sometime, I suspect a vacuum leak, tell you what I find.

Do you have a manual? If not, there are a couple of places that have them online. The BAC is on the drivers side of the intake plenum.
If you just had a rebuild, it could be a leak in the intake manifold connection. Spray some starting fluid around there and see if you see some momentary surging. Also, I've had problems before like this when i removed my intake because when i put the throttle assembly back together, my throttle plates were not closing fully at idle causing some rather strange behavior. Regardless, it is an air problem.