I'll not pretend that I know much about the VW/Audi 1.8t but I'm trying to learn slowly.
Last week I had my Mk1 180 remapped by a local bloke, supposedly to 211bhp but it hasn't been dyno tested so it's purely a guess. All was well and I was enjoying the obviously increased performance but today I got in and had very little boost. Torque app on android seemed to suggest boost but it just wasn't happening.
Just tinkering around as I do and I pulled the little vacuum hose off that goes in to the top of the diverter valve. Suddenly I seemed to have my boost back. I didn't drive far like this as I didn't know what the effect might be but it definitely seemed to help.
I don't know what this indicates as I don't know enough about the operation of the diverter valve. The last turbo charged car I had was a Fiat Uno Turbo in about 1990 and it had a mentally huge dump valve (fitted by a previous owner) !
I know what the diverter valve does per se but I can't quite get straight in my head why removing the vacuum would make boost come back. The vac hose has a negative pressure on it at idle which I presume (?) then becomes positive pressure when under boost, closing the gate to allow the full pressure to the turbo.
Is there other stuff that I should be looking at instead ?
Any advice or pointers appreciated.