Originally Posted by Hawg Driver
Always open to other ideas out there…
Sounds like you've eliminated ignition, which leaves fuel and air.
How do the plugs look? Oily or dry and grey? Might give a hint if it's getting too rich or too lean.
Have you tested with no air filter?
You might also try a fuel flow test to see how many GPH your electric fuel pump can push out. You might also see if there are some bubbles in there, supporting the theory that there's air getting sucked in.
I'd also check the fuel tank vent lines for mud daubers.