MAP sensor was changed to wideband to account for the positive manifold pressure. Suzuki used the same setup with turbo. It's only boosting 5 to 7 psi and the surge happens before it even spools up.

This system and motor are being used in a homebuilt airplane that also has a turbo added. We think the issue (mid RPM surging) is O2 related, but not 100% sure. The exhaust had to be shortened for...