Mk4 golf gti boost problems

[Newbie gti Nick]

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.

[lemski]

 Have you scanned.
Id swap out the recerc valve for another to rule that at

[LR5V]

Yes - scan and check all your pipes:

breather -they dissolve from the inside out
vacuum -just turn to dust
boost  -dependant on your engine the spigot joints start to leak

[Newbie gti Nick]

Thanks for reply.I took the dv off and checked it by sticking a 3/8 ext bar in it and finger over the top and the vacuum seems fine. Have a cheap scanner the only code I seem to have now is the dreaded 17705 leak between turbo and dv. But before that I've had these which aren't coming up anymore 17545 and 16795. But drove fine even with these. The bottom oil breather seal was leaking so I replaced that.

Cheers

[lemski]

Id try a dif dv. Or be checking all clamps and vac pipes.

[Newbie gti Nick]

I'll order one up and give all the pipes another good check over.
Cheers