I have a blue top fitted with an Ivoprop ground adjustable 3 blade prop. Even wìth the prop fined, we can't get over 5900, which then drops to 5400 over 10sec. Fuel pressure good (Facet fitted for boost) needles and jets correct, plugs 2 hrs old, pots give full lift. Tried bigger main jets - no go. Pipes all new and tight. Getting despondent. Anyone help?