wheres a good company to send my 454mpi computer off to get some tuning work done for headers?

Arizona Speed and Marine have been doing it for a very long time.

With an exhaust change only, you shouldn't need a reprogram. Merc engines are rich to start with. I've got CMI's on my 502mpis and don't believe the ecm's were touched.

What year is your engine, and do you want to run 87 or or 91 octane? They have very conservative timing, so headers, rpm limiter bump and more spark can sometimes yield some good results. The 502 is the same way, could use a little tweaking, epecially leaner in part throttle area's for better fuel economy.

Dustin

Dustin, lets do a switch out on computers for the 525 so I can see results?