[doughboy]

Sparky,

Personally I doubt very much if its got anything to do with the DVs.

There's a lot of BS about DVs. Firstly remember DVs don't 'hold' boost. When the throttle is wide OPEN, the same boost pressure is present both sides of the DV (charge pipe boost underneath and manifold pressure on top). It is only as you close the throttle that a lower relative pressure occurs in the intake manifold and 'sucks' the DV open. The DV spring is only there to control the opening point, not 'hold' boost.

My forge DVs open at the correct 300mbar vacuum (same as factory units), this means they will 'blow' open with only 4.2psi of boost from the charge pipe. It is only the boost pressure fed back from the manifold to the top of the DV piston (via the small hose) that allows it to stay shut.

So even at 1,000,000psi of boost, as long as WOT the manifold is at running above 999,996psi then the DV will stay shut.

If it really was failing DV diaphragm you would more likely show OK boost up to standard, then it would drop sharply as they failed and leaked at higher boost.

Your's isn't doing that, it is low boost lagging way behind target from the outset. I would think vacuum system or actuators.

BTW you can't smoke test a vacuum system, smoke test are for positive pressures only (so the smoke comes out of leaks and you can see it).

If the bloke did indeed do a positive pressure test on the vacuum system, then a) it could damage things and b) its meaningless as push-on vacuum seals will leak like seives at positive pressure.