Hi all My 221 does not make the proper amount of boost through the rev range. Some thoughts are that there is a boost leak and I am trying to test for this. I am using a boost tester which is is basically this: I have 2 of them (one for each turbo) but am only pressurising up through one. I found a few leaks, but something struck me as odd. All the info says to start with the compressor set to 5psi and then work your way up to full boost pressure. I could not build any pressure in the inlet side of the system until I turned the compressor reg up to 80+ PSI. I Initially think this is due to the restriction that the tyre inflation valve provides. Even then, I could only build 10Psi in the inlet system. (I had a few leaks but nothing gaping!). I believe a few one way valves are leaking as well, so have ordered replacements. Obviously some air will leak past the throttle body, but is this normal? I though this is probably due to a large volume of air being required, but not so sure now.