When does it fart and pop; all the time?
If its too much fuel, and you swapped out ECU's, then something like high f.pressure, as per Ash's suggestion could be a good bet. Im guessing though, you've checked base.
Its not some kinda SR freak out mode, caused by something not plugged in? Error codes?
Ha, i thought that too I'm sure he juz has a lot of mates with tractor motors I mean SR's.
Got me stumped, so I'll do the blanket "more info" warcry