I think that at the meager 5.5psi the turbo was well below it's efficiency range to support the CFM demands of the 3L at said atmospheric pressure.

The map for your turbo shows it should like 9-14psi range the best. (14psi - stress testing at it's finest I tell you - You chicken )


Maybe if you had a mere 2.5L then 5.5psi might have been sufficient.

2000 SVT #674 13.47 @ 102 - All Motor! It was not broke; Yet I fixed it anyway.