I went and did speed runs this afternoon, plugged them into the kitplanes spreadsheet, I have a calculated IAS correction of +3.9, so thatís part of the answer.
But I discovered something else doing research on MAP gauge calibration. Reading this thread here
, I calculated that my MAP gauge should be reading 28.95 with the engine off. Turns out itís reading a hair past 30.00 with the engine off, so I have been thinking I have been flying around at ~65% power, instead it been closer to 58-60%.
So OP, double check your manifold pressure is reading correctly, and from several other posts, just cause itís electronic sensor or EFIS doesnít mean itís any more accurate or calibrated than a mechanical one.