Struggling with idle
I am sorry for putting up a thread that has been beaten to death, but the search function didn't really show me anything new. I have been experiencing a rough idle for about four - five months now and have tried and replaced so much that I'm beginning to go insane. Sitting at idle the car feels like it has a vacuum leak and when accessories are turned on it drops significantly, sometimes dies, and then goes right back to the crappy idle. Under throttle its completely fine and pulls all the way up without issue. So far I have replaced all of the following: IAC (motorcraft 3x), TPS , MAF, Vacuum solenoid, EGR, throttle body, PCV, all of the tubes connecting the valve covers to the intake (including adding a JLT oil separator), handheld can tune, dyno tune (fastlane), upper plenum, header gaskets, intake manifold, alternator (PA performance 130amp) and the vacuum line that runs into the passenger side inner fender from the back of the plenum. I have tried spraying carb cleaner on different spots of the engine and traced every single inch of vacuum lines but had no ideas. I am at the point that I am about to rip the hair from my head it is driving me insane. The modifications to the car include: JLT RAI, Kooks LT/catted x, flowmaster cat back, FRPP intake manifold (stock replacement from LMR) Trickflow plenum, Trickflow 75 mm TB, dyno tuned by Fastlane Performance in Benson, NC. There are only 80 thousand miles on the car and it was completely stock when I bought it. Again I apologize for the super common topic and I really appreciate any help .