I have the same ECMs. I was asking because I want a pair of MEFI4B's & these are not 4b's.
They are 3's which I have. The tune or program on them is of no concern to me. I'll wipe it out & do my own, which is what we did on the computers I have now.
This same Delphi number ECM is used on TONS of stuff from GM crate engines to Mercruiser & Volvo powerplants. They are not anything "special" as just the ECM.
As far as the 4 mph gain. I suppose if all the stars aligned properly it could be possible. Merc sets their stuff up on the rich side so by leaning it out & raising the rev limiter it is in the cards.

Ecm's Sold! Thanks Guys

I have a set of recalibrated ecm's also if anyone needs them.

Whatcha want fer'em?

Mefi II's 500.00