Andy I had a primastar in a while ago with a lack of power, first the EGR was stuck open, so thought great quick fix, the van was just as bad lucky to get to 40 mph, no codes stored. After a lot of messing around I replaced MAF and it was about 90% better I was not totally happy with it, but i scoped the MAF and FRP on a snapped throttle. Pic below is with a new MAF and EGR the response time on mine was 1.7sec i questioned this myself, but from my experience its a good response time...

Have you made sure the MAP sensor is reading correct and these do suffer with turbo issues...


Known good MAF v FRP

Darren