90 keeps backfiring

Ok I have beat my head against the wall here... now I need some help. I have a problem with my 90 popping (backfiring) through the breather... it doesn't do it all the time. I have checked the resistance readings on most, if not all the sensors, nothing real bad. The intake temp was couple hundred ohms high. I have replaced the distribuator, the tps is reading .85 volts and has a smooth sweep. One odd thing to me is I have replaces the IAC, but when you unplug and replug it does nothing (no humming or vibration like it isn't doing anything). When it starts popping I can kick it down out of overdrive and she runs good till it goes back into 4th gear... Short of replacing all the sensors, what kind of suggestions do you all have... Something has got to give with this jeep! :dunno:

Well this has gotten long, so what you all think?

Thanks for the help.

Kdplyn

This might be a good time to replace your CPS.