Missing boost!

[RichardE]

I posted a while back with a boost cut out problem and with everyone's help we traced it to a faulty boost switch. Probably as a result of the violent cut outs we destroyed the rubber centred clutch so the car went into the Porsche workshop for replacement.
When I got the car back I noticed the temperature and oil pressure gauges were flickering, especially over bumpy roads. Fuel and oil level ok in fact all other instruments functioned properly.
I also noticed that the boost gauge won't go past .6 bar.
The car is a 1989 LE so it is a European RHD version with basically all the 930SE engineering but different front guards. As a result it should have a 1 bar spring and before it went in it certainly spooled up to the end of the gauge which reads to 1 bar.
Now they say they can't find anything wrong but under boost it doesn't feel quite right. I am sure both fuel pumps are ok and air seems to be ok.
I assume somewhere there must be a loose contact causing the gauges to flicker, but could this be in any way related to the new boost switch?
I can't work out why the car boosted to 1 bar before hand, the engine gets dropped out and put back and now won't spool right up?
Weird.
Is it possible the new boost switch is not compatible with the SE type engine?
Could the boost gauge be faulty? Like does that ever happen?
The engine revs to the red line but boost stops at .6 in second and less than that in third gear and then I can't find enough space to go any faster!.
City dweller!
Maybe some of you clever guys have some ideas. Thanks.

[9dreizig]

from what everyone says, the boost guages on our cars are so bad, that it could be the issue. I suggest a mechanical guage for a sanity check. Mine won't go past .6 either..

[beepbeep]

1. boost gauge is fed by electrical pressure transducer, it only feeds the gauge and cannot affect boost in any way. If it flickers, it's probably bad or electrical contact to it is dirty. Clean or replace.

2. boost cut-off switch is on/off device that kills power to fuel pumps. It either works or it don't. It cannot affect boost in any way.

- Measure boost with manual boost gauge. Take feed from intake if possible. If still 0.6 bar, check if you have leak somewhere. Usual places: Intercooler O-rings, phenolic spacers and their gaskets.

If that checks OK then you probably have stock wastegate that was previously fooled into boosting to 1 bar trough leak somewhere. Maybe they re-sealed the wastegate feed line so it now works at it should. Either that or wastegate might be leaking.

[911st]

If there is a leak in the intake system under boost it is difficult to find when not at boost.

Typically what happens is the inter-cooler to throttle body seal will fail or leak.

Try reseting the inter-cooler and or replacing the seal.

[RichardE]

Thanks for the help you guys. I will get my service guys to check your suggestions out. Much appreciated.