cause of loss of rpm

[sands]

I posted this in the technical section but I was hoping you guys could help me. Last year after winter layup, I had to drain about a gallon of water from the gas tank. Looking at the filler cap, it appeared the gasket was thin so i replaed it with a bigger one. Underneath the cap there was dirt which appeared to be from run-off water during the winter. I assumed this was the souece of my water. Any of you had problems with issue and do you think i'm dealing with the same issue again.

Thanks, Joe

I own a 1999 pantera with twin 502 efi's. Late start to season and had the water pumps, distributor, cap, and plugs changed. Ran right around 5000 rpm's last three years with gps reading between 76-79 mph. This year, port motor max rpm's right around 4200, starboard max around 4400 and I can only reach 64 mph. Engines don't seem to be running rough. Any ideas.