I've been involved with a chaps 2003 vauxhall vivaro 1.9 van last week. Basically he had been to several garages who couldnt fix the fault. No EM light on but would suffer from lack of power when setting off. It had no DTCS stored, a quick check of the live data fuel pressure, egr,boost and MAF. everything looked ok apart from a lazy MAF reading, it should of gone above 350 when revved but was only reaching 220. I checked the airfilter as these are common for been sucked in or blocked.. all ok. removed the EGR and checked that.. all ok
I then took a capture of the MAF which looked very low....
Yesterday i fitted a new siemens unit and retested.. the green trace is the new MAF
Took it for a run with the chap and he was over the moon! his van was finally fixed!
please feel free to use the attached files to compare with your suspect MAF