I am having issues with lost boost (3psi) on my MP62 HS with air/air ic. 126/65mm pulleys. Been at the dyno shop and the boost and power is down. Boost loss 3-4psi at peak torque. The blower has only done maybe 10K ?. They checked for leaks and found none (pressurised the system). On doing a compression check (185,190,185,160). Leak down test on #4 cylinder was 22% other cylinders 2-5% leakdown. On removing the blower manifold found that some rotors had gray teflon coating completely missing but rotors looks smooth with no abrasion.

What is causing the boost loss ? is the teflon coating for boost/efficiency ? others have said its just for honing the new rotors in ? We found that #4 exhaust valve was stuck open - could that be causing such a loss in boost ?