so ive been having this problem for a while now and ive tried everything i could possible think of. I have a 94 3.4l automatic and its having a rough idle and a check engine light thats going off and on.

the codes came up as the EGR, IAC, and TPS so i replaced them. That lowered the idle from about 1800rpms to 1500 rpms in nuetral/park and to about 1000 rpms when in drive. so my next though was tune up/vaccum leak. so replaced the wires, ignition, and plugs with performance parts and triple checked everything. she ran way smoother but still the idle and check engine light came on and off. when doing a vaccum check i discovered that there was a great amount of suction coming from the area were you put oil in and also that when i choked the Throttle boddy the engine was still running!!! i choked the PCV air in tube and the idle dropped to 800 in park. I must add that the A/C is not blowing cold and oil pressure gage will drop to 0 some times when not on the gas. any ideas of whats wrong would be amazing thanks

Update:PCV valve is working and my next guess is bad CAT? theres some rattling coming from under but an exhaust shop said a bad cat wouldnt make the check engine light come on on my model. He may be right about that? but if the cat wont come up mabya bad cats causing the EGR to come up?

help plzzz