Hi
Yes - they are intertaining engines to play with !
You could try one thing though: i experienced that my FTLP - fuel tank lid pressure - was much lower than the actual fuel pressure.
I have solved it on several Genesis and Nemesis by simply fitting a rather strong spring ( like 6 mm diameter ) with a metal hook to hold down the fuel tank lid.
Image that your engine is racing away with 30,000 rpm and the fuel tank lid opens sligtly: fuel pressure drops immidiately and engine runs lean - ie dropping rpm at once. When rpm drops, exhaust pressure drops and fuel tank lid close again and engine runs and sounds normal..
Give it a try mate - it dosent cost a lot !
Best regards from Denmark
Niels Vangsoe
www.nitromekanikeren.dk