[rotrex]

For intake restrictions it is best to measure pressure level before the SC intake.
From this value and boost pressure, you can calculate the pressure ratio.
Any cheap vacuum gauge or boost gauge will do. If you see more than 100 mbar of intake restriction, investigate. At a pressure ratio of 2, a 100 mbar intake restriction causes boost to drop by roughly 0.2 bar. 2 = 1.8 bar / 0.9 bar. At 200 mbar, you get 2 = 1.6 / 0.8 = 0.6 bar of boost or 0.4 bar less than without any intake restriction.

Intake restrictions usually show at high air flow, so near max rpm and WOT.


With this and SC rpm you can look up the corresponding air flow in the compressor map.

This number should fit reasonably to air flow you calculate from AFR, and fuel flow derived injector size, injector duty cycle and differential fuel pressure.
The calculated air flow should also fit to your power level. If you burn much more fuel than you'd expect from the power the engine generates, you indeed might blow fuel out of the exhaust during overlap. At 5 to 8 PSI and high rpm this is usually not too big of a problem.