My 88 900 Turbo runs about 25psi at max boost. I recently fitted an MSD ignition (to the twinaabs.com recipe) and noticed 2 things immediately after fitting.
1. Better fuel economy (up to 34mpg average from previous 28mpg)
2. Improved boost stability with MSD boost timing master allowing for greater retard.

Along with the improvements has come a new problem - acceleration is great but when you ease off, the turbo does a sort of "stutter" as what I imagine is the backpressure may be too great for the bypass valve to deal with. Does that sound right? I have fitted a Forge bypass valve as used on the Audi TT - its the type with the screwed body - FMCL007P.

Needs more Ppppppppssssshhhhhhhhhh!!!!



*I have no idea what I am talking about*

Well, greater retard wont provide more power (actually the opposite), but that wasn't what the question was about :)
The valve you've fitted should be able to cope with the alteration in ignition, as the boost is the same, correct?
Ohh, yeah, maybe this should be moved to the 'mods forum instead of the project-forum :D
Daniel