my 94' w/4.3 vortec CPI-w has become a major disapointment!
it has 105,000miles recent tuneup/plugs, wires,cap,rotor,fuel filter
It revs up and down violently at idle, and seems like it wants to quit when you let off the gas. The problem seems to be intermittent, it runs like crap for a couple of days and then it tends to act fine. I have a cheap scan tool, but by the time I get a chance to plug it in, the check engine light is off and it reads no problem. PLEASE HELP this is my daily driver and I know it will get worse.

check the EGR valve and the CPI injector in the upper plenum.

Serch the foeums for how to do it.