I have quadra 75 in a ziroli corsair has a Menz 22-12 prop and the highest rpm's I am getting is 6500. I have flown this plane seven times and everytime it flew after 4-5 minutes it dropped RPMs/power in the air and I had to land. I then changed the fuel tank and all the lines. I also checked the diapram and the screen. It has a simple two line system with a vent and T-line. The fuel tank is wrapped in foam. The highest I can get is about 6500 with the 22-12. After running on the ground for 1 minute it surges for a second a couple times like its getting air bubbles. The transition is flawless. It also has plently of cooling in the cowl.

The needles right now are 3/4 high end
2 low end.

Any suggestions??? I am about to unbolt and send to b and b for a check up...

Thanks
Peter