what is the leading cause of backfire on decel?

[blinkshome]

the smoking finally stopped from the turbo w/ a restrictor from the oil intake (.063). when i wind down from a high rpm ill get a bubbling backfire below 2200 rpm. it will blow a puff on these low backfires. not all the time, half the time. time of day has no relevance. what is the leading cause of backfire on deceleration?

[480sx]

The temporary super-rich A/F ratios associated with having a VTA type blow off valve. Basicaly what happens is your mass air flow sensor takes a reading of all the air that pass's through it. When your blow off valve goes off on decel letting the same air that pass's through your MAF out of the system. So your ECU thinks its got extra air in its system and it sends the fuel needed for that much air.

If you recirculate your BOV your stumbling problems will stop.