For all the guys who have experience tuning:
I have the MEFI software from MEFIburn and have been working with a turner and we are making progress.
One issue we have had lately is a surging at 2100-2400 when getting on plane and again at 3400-3600 range. I can push through these areas and the motor runs fine.
I am running a wideband with 02's as well. Air fuel ratio is about 11.5 at idle and 12-12.5 through the rpm range.

Any idea what tables to look at for this issue?

My motor is a 99 Stock headed MEFI 509 with a vortec supercharger, stock inj, TPIS TB, Cam i believe is stock but, could be slightly bigger, Larger mercury exhaust manifolds with gil 4" risers.
I have a upgraded fuel system Aeromotive marine 1000 pump, high performance filters, water separator etc.

E

Which MEFI do you have? 1,2,3 or 4? Likely a 3 or 4 but important to know.

Was the tune on the MEFI stock before you began messing with it?
Do your RPM/MAP/BPW cross over values between the 3 fuel tables match? (they must be identical)
Do the same check for your spark table. Variances in spark advance can cause an issue like your are seeing. Make sure your spark table doesn't have an odd or out of place value in one of the cells. I did that once.

I HIGHLY recommend keeping things simple and only play with the fuel and spark tables. Don't mess around with scalars, flags and constants....99.9999% of tuning is in the fuel and spark tables WHEN transitioning from stock to modified.

Trash, Mefi 3 ecu. It had a custom tune when I bought the boat. It was way rich down low and needed tweaking. Unfortunately I don't know who tuned it last so we had to erase the file because we were locked out and created a new one. The boat has run better over all but we just need to tweak it to eliminate the surge