I am at a point where I need to do valve springs on a 502 mag mpi , and like everyone else , a little more horsepower would be nice. My worry is getting the correct tune. I am wanting to do a cam and head swap. My boating is mainly in saltwater but I did install a half closed cooling system. Does anyone have a proven combination to where the tune is straightforward? Thanks in advance.

In all honesty, the factory tune is so rich that you can add 100 hp and most likely be ok. Just add an O2 sensor, which you will have to install to tune anyway. It is pretty easy to do yourself with the mefi burn software