I have a 93 z28 lt1 104k I purchased a few months ago and has hesitation problems when it is warm ,at a stop sometimes it will idle up and down within 200 rpm ,from launch it will stumble and cruising it will stumble from 1700 to 2300 rpm after that the car does not hesitate at all. I recently changed,optispark,10.2mm wires,ngk plugs,msd coil,water pump,160 thermostat and map sensor because I was told by several mechanics this was the problem? well it did not do anything but cost me money! car has jet stage 1 chip,3" flowmaster exaust and k&n air filter system installed by previous owner.I have checked all vac lines and replaced some and have been running high octane with injector cleaner.This is my 1st time using this site and I would greatly appreciate it if someone could point me in the right direction. THANKS,BOB

(OLD PLUGS WERE BURNING CLEAN, EVEN THE #8 PLUG THAT THE PREVIOUS OWNER COULD NOT CHANGE ,LOL

 

make sure everything that has to do with your intake is clean. throttle body could be sticking, clean it, MAF could be stopped up, CLEAN IT, and as far as the idle going up and down, as much as I'm sure everyone is tired of reading it, CLEAN THE IAT SENSOR WITH THROTTLE BODY CLEANER!!!!

 

might be worth pulling the jet chip to see if thats it.