could well be plugs mate. how much boost do you run? ive heard that due to the nature of the fuelling, the higher the boost equals the higher fuel rate required which is obvious. except that mfi means the onboost fuelling been spot on leaves the rest of the range rich. as its all or nothing. theres very little if any scoipe for fuelling both on boost AND mid/partial throttle openings. as a result the plugs have a hard time.
while the spark appears healthy when checking (under no load/compression) it can easily be overlooked. things are alot different under compression and engine loads. its worth checking leads/connectors anda general looksee through the possoible culprits. easy way is to remember the basic rule. an engine needs air/fuel/ignition. if you have fuel and assuming a pigeon isnt living in your airbox then id look at the ignition side of things. a check of the timing may be worthwhile for elimination purposes.