Are you tuning these yourself? Stock ECU bench flashed? The biggest limiting factor seems to be the tune on most of the setups. That and the fact the 4 Cylinder motors dont get enough love and attention they deserve as you too notice. I like them very much. they are nice little guys.
Maybe if we ever do a M122H setup on a 4 Cylinder, you could try it out since you are into High HP. that thing by itself will put out more than what the current setup combined does.