Pop off valve clanking...Low Boost at High RPM

[ewave]

Hi,

After not using my 930 for a few months I go it back on the road. First I had to rebuild the fuel distributor as the control piston was stuck with varnish.
(Control Piston seized on Bosch CIS 911/930 Turbo)

Now that the car is running I have two concerns:

When blipping throttle from idle, I can hear a clank when I lift up off the throttle. I had someone rev the engine while I held my hand on the pop off valve, and that's what it is making the noise. I do not remember this happening before. Is this normal, or is there something I should check?

Secondly I can get full boost (0.80 bar) from around 3500-4500, but then the boost starts dropping off to about 0.60 up to redline. Also there is _slight_ rattling/pinging under full boost like the car is running too lean.

The control port on the END of the waste gate is vented to the engine bay, the other port is hooked to the regular pressured output on the inter cooler.

The auxiliary air pump/air injection and associated plumbing was removed over ten years ago. Everything else is stock with the exception of an aftermarket exhaust system. (I think it's a FabSpeed)

Any idea what I should check? Any help/comments would be greatly appreciated.

Obligatory picture...

[A930Rocket]

See the thread above. The silicone seals are shot in the recirculation valve.

Check all your hoses and o-rings for leaks. Are you relying on your stock boost gauge? They are notorious for being wrong. Get a good mech gauge to replace the clock.