Zinger

I looking for someone that knows about A 500EFI ecm model 840136T2. I have a set-up but no harness or ECM what are my other options?

GPM

Aftermarket, probably easier to tune

articfriends

iTrader: (1)

Yep, theres virtually no mefi3s to be had left out there. or virgin harneses, if you find one, buy it! A used mefi3 programmed for a 500 EFI is 1500$ these days and most harnesses are hacked up or few and far between. Take that 2000+ $ your gonna sepnd on used electronics anbd buy new, Smitty