Long story but will short it - my car (Audi TT 1.8T - 165kW) has no boost or very very low in low revs (in 3000 - 5 psi, 4000 - 10psi), with peak at 5500 rpm and 14.5 psi, at 6720 12 psi. Car is re-mapped because requested pressure is 21.5 psi _ bought it like it is now.

Tried new N75, MAF, done leak test up to 15 psi -no leaks ..... no change. :(

So .....I have decided to test again my DV. I pushed the piston of the valve upwards against the spring (it moved without restriction). Then with the piston pushed fully up, with the spring compressed, I placed my finger over the top nipple to form a

seal. see photo 1

Then I released the piston, keeping my finger in place but piston moved about 5 mm down - see photo 2

After I removed my finger from the nipple, at which point the piston travelled another 2 mm back and made noise (shoot).

Here is re-assembled DV - I don't know what type is it - it was on the car when I bought it.

I have tested it maybe 10 times with same result. Dost it working properly or is it faulty? When type/brand is it?

That sounds fine to me, as long as it holds a vacuum with your finger over the top nipple it should be fine. It's not forge but possibly an ebay one?

If you have the old Bosch one pop that back in. This one may not hold enough boost as we don't know what spring rating it has yet.

That sounds fine to me, as long as it holds a vacuum with your finger over the top nipple it should be fine. It's not forge but possibly an ebay one?

If you have the old Bosch one pop that back in. This one may not hold enough boost as we don't know what spring rating it has yet.

Haven't got Bosch because I got it with a car I think it is Hyperboost HXC DV but I am not sure. Actually I haven't got much boost only 15 psi peak - could be a weak spring?