Well after fighting the MEFI for long enough , I am going to convert to an AEM Infinity 3 ECM with AEM's kit with plug n play harness .
Time to move forward in Technology!
Unless you have the Software from GM , its cumbersome at best tuning the MEFI. The Infinity Tuner is very intuitive and full featured .
It offers real time tuning with the option to save or revert . The tables have more resolution where its needed . Also does self learn with 2 Widebands .
Looking forward to dynoing this set up , I'll post results.

Would you be interested in selling you MEFI 4B Computers?

for 450 bucks per plug on play harness,,I'd be running a new harness or repin the mefi harness.but hey,let us know how turns out.

Are these ECM's supported in a marine application

The harness is alittle pricey , but its a time issue , customer wants the boat back to do more mods , or I would have built a harness. All in
I have less than 1600.00 in the ECM and Harness. They are Marine Rated , the molex connector on the ECM is the same style that Seadoo uses on there ECMs.

I have a mefi 4A ecm I'd sell and those AEM's are not holding up in the marine world.

Ever buy this and run it? Does it have provision for gm.flex fuel sensor, still planning my personal 13-1 548s for my boat (E-85)

Yes , It works great , the Harness is built by Alexi at boostpower. He uses the AEM ECU on all of his engines.
I have it on a customers 572 , 4.0 whippled engine . Tuning and Data AQ are really solid , its more engineering based and can get alittle complicated.
But he has over a 100 hrs on it. Yes it will do Flex fuel. It is used alot on E85 apps.