okay, i have been working on my runner for several days trying to diagnose several issues. they may all be connected for all i know. if and only when i hold my rpm at 1700, it will pulse back and forth between 1700-1500rpm while parked. sometimes it will even jump to 2200rpm then back down. i am also having random backfires out exhaust, and my acceleration at highway speeds is not upto par! other than that it seems to get around alright with minimal studdering/hesitation. No Codes Either!

I have replaced:
distributor cap
rotor
vaf
plugs
oil & filter

Any Ideas?