I have a 91 rs, I have rebuilt the TB, put on new map sensor, IAC, TPS, new Vacuume lines, catyletic converter is empty, checked the fuel system charcoal canister and relay, all that stuff is operational etc.... it still continues to Idle up and down w/in 200 rpms and then stalls....on top of that it has started to backfire occasionally and stall more often...what could I have missed? anyone have any ideas?? When I put this new motor in a couple years ago it was fine for about 6 mos maybe a year. Think valve lash needs to be readjusted?, I have pondered blocking off all the smog related items. surely someone has run into this........

 

Hook a timing light up to it and see what it reads, and checking the valve lash could help. I've been fighting with those 2 things on my motor forever.

Good luck!