OK

After 10-15mins of driving, im noticing the boost guage is reading about 10 inches of vacuum in the manifold (at idle). It should be sitting somewhere around 19-21 inches. Also struggling to hit 5psi under boost.

I would have thought if there were a massive vacuum leak, the engine would idle like s**t and run very lean. But no - engine is running great and air/fuel is remaining around stoich. Impossible to tell if i'm losing power under boost - my seat of the pants meter not accurate enough.

I'd like to point the finger at the gauge but that's a little naiive!

Will be inspecting for vac leaks on weekend, anyone got some good tips for doing this on the windsor? Will prolly dismantle all vac lines and check, but i think i should also look at the upper and lower intake manifold... which looks like an absolute prick!

could your gauge be f**k?

Fingers are crossed!!! lol

Yeah im thinking this may be it... its not responding properly (not reacting to small movements in throttle, only moving around when i PLANT accel).

But want to ensure manifold vac/pressure not being compromised - this is how i make my power

as for finding vacuum leaks, grab a can of aerostart and go nuts!

does your vacuum gauge have a pressure line or sender? if its got a pressure line, it may have rubbed through somewhere, and this would be enough to slow the gauges response and limit its readings

Yeah, good call. Its got a pressure line coming thru the firewall. I'll yank the lot out and make sure there's no damage to the line. Lol, little hard to avoid running near the exhaust on a V8!