lsc91

I know I posted something about this before but I really need to fix this problem. Its an 88, 4.0L with 233000 miles and I just replaced just about everything you can. I did a complete tune up, meaning plugs, cap, rotor, wires, fuel filter, air filter, and oil change along with map sensor, IAC ,factory EGR valve, TPS, and O2 sensor. While doing the tune up I also did the valve cvr gskt and cleaned the crap out of it and the pots. I tried adding an octane additive and the higher drade gas but its still there on occassion. Is there anyone that can make a suggestion. Please help and thanks in advance.