2006 Turbo S with EVOMS air boxes and diverter valves, Fabspeed exhaust and ECS tuning, 90k miles.

I have an intermittent problem with losing boost: it comes on strong and the boost gauge is pegged (>0.8 bar) then immediately drops to 0.4 bar and power falls off accordingly. Other times it holds full boost and goes like hell.

It was also misfiring on occasion; I replaced the plugs, coils and MAFs. No more misfire but the boost issue remains. Vacuum lines are good.

I've read similar descriptions here and on other forums but no definitive answers. Anyone else have this problem, and able to fix it?

Thanks in advance!

 

I have a 2006 Tts. Same issue. I found that the evoms diverter on the drivers side was sticking open. Yes the one that is a ***** to get to.