Update to: 1.5 bar cutout on unchipped 5kcstq

[Wallace White <wallace@remdesign.com>]

I received many good suggestions about what to check regarding the
overboost problem I had a few days ago. Thanks again to everyone who
replied!

So, the wastegate diaphragm seems to be intact; I hooked up the Mityvac
to the hose from the wastegate at the WGFV and it held vacuum. Of the
other two lines connected to the WGFV, which is normally open to top of
the wastegate? I see from the Bentley that the bottom of the wastegate
has a hose to the intake manifold, and that the WGFV is connected to the
intake manifold and upstream of the turbo. While I get the basic idea
that the WGFV applies pressure to keep the wastegate close, I would love
to hear a good explanation of the arrangement. Anyone?

I also hooked up a test LED to the WGFV terminals, to observe its
cycling while driving. The LED showed that the WGFV was being cycled at
WOT until manifold pressure built up to 1.2 or 1.3 bar--which is normal
operation, right? If I stayed on the throttle, though, the manifold
pressure (on the stock gauge) would reach 1.4 or 1.5 bar sometimes. But
the fuel pump didn't cut out, as it did a few days ago to start this
thread. I did several runs that levelled out at 1.5 bar indicated, with
no cutout. Maybe I shouldn't be complaining!

So if there were a real leak in some part of the system, forcing the
wastegate shut, wouldn't the boost build up to 1.5 bar rapidly and then
the fuel pump would cut out? My car is building up to 1.5 bar and
staying right there. Or would a small leak cause this slight increase in
boost--which happened to be enough to hit the fuel pump cutout a few
days ago but didn't happen to be enough in my runs last night?

Thanks to all for your help on this.

- Wallace
  '87 5kcstq 152k