[Gaz64]

This is starting to sound like a restricted needle and seat issue.

If the fuel pressure does not vary below say about 4psi at WOT, AND it occurs anywhere in the rpm band from 3/4 throttle up, then main jet changing that doesn't sound like they are making differences points to fuel supply trouble to the bowls.

Fueltank venting, all hoses and lines for kinks, pump capacity, fuel filter capacity, fuellog, regulator etc.

One of mates had trouble a day after he changed a fuel filter, I found fuel line rubber in a needle seat.

Gary