496 mag fluctuating Rpm , while going fast
 

Both motors run all day 3000-3400 rpm, if i hit the gas slowly bring it up around 4k. Port motor fluctuates rpm down and up rapidly like its bogging. But runs fine at slower speeds.

Fuel filter replaced?

What's your serial number?
Might be a fuel restriction filter as Rookie mentioned, the anitsiphon valve, or weak fuel pump or boost pump (if there is one)

Put a pressure gauge on the fuel rail

Start with the basics. Change the spark plugs and fuel filter.
A friend had similar issues and replaced plugs and wires and all was good.

plugs and wires brand new and water separator filter, i will check fuel pressure at rail and while its running. thanks bob

I can't promise this is your issue, but Crankshaft Position Sensors on the 496s can present RPM fluctuation issues and not throw an error code.