Hi all, my Corsa hasn't been boosting right, it's underpowered and the boost can feel a little bit notchy. I have replaced a load of parts and everything seems to improve it slightly but it's still not right. New parts I've installed:

- Pipercross air filter
- Bosch Maf sensor
- Bosch Map sensor
- Brand new genuine k03 turbo with new actuator and new turbosmart recirc valve (my old turbo had a lot of shaft play)
- NGK Spark plugs
- Delphi Coil pack
- Oil change
- Bypassed the rear bcs
- There doesn't seem to be any boost leaks, though I haven't done a proper pressure test on it yet

-Compression on all cylinders showing 175-180 psi.

-No codes showing on a Snap-on scanner

Any ideas? Thanks!