2004 mercury 60 hp Bigfoot 4stroke running rough at higher speed

I have a 2004 4 stroke 60 hp fuel Injected mercury big foot on my pontoon boat that will start running rough and almost die at high rpms. Like it's starving for fuel I've checked and cleaned the fuel filter. Replaced the fuel line from the tank to the motor including the primer ball. And also checked all vents for obstructions. After I did all that it ran fine for a couple days but now it is doing the same thing again and I'm stumped. If anyone has had this problem before and or has any thoughts on what could possibly be going on that would be great thanks in advance for any help or advice you can give. 

I would also look at the pick up line inside the fuel tank if you have one. It's possible you may only have a nipple on the exterior of the tank. One small piece of debris may be enough to obstruct your fuel flow.

Thanks for all the responses and yes it is fuel Injected and has a primer bulb still but no choke 

Could be as simple as bad plugs or coil starting to fail.  Try a different fuel tank with fresh gas after you have changed the plugs.  

Chopper…marine gas??  I don’t think I’ve ever seen marine gas at any gas station 

And to the whip guy…OP said he had fuel injection, doesn’t that mean no primer ball???

Couple years ago I let mine sit over winter with only a 1/4 tank of gas, didn’t realize till the next spring and after running for a bit had the same problem, changed the plugs and all was fine.  Bad, old gas??