I'm new to all this so apologies up front.
I have recently purchased a 1.8t aum mk4 golf.never owned a turbo before.
It was having idle problems. It has had a new maf fitted pcv bypass and n249 bypass. Ran well for a week.
Now boost seems lower,but if you lift off throttle and push back down it'll boost higher each time untill the boost gauge just passes 0.5bar then the needle sort of chatters there untill lift off!(Sounds weird). It also seems to be releasing to atmos(standard dv) sometimes it's jumpy through the revs when reaching 3k upwards.
Could this be the n75 valve?
Help would be hugely appreciated.