Was trying to breathe life back into my old Coverite .40 size Gee Bee Sportster Model E. Had installed an ASP .40 with a modified Tatone Pitts Muffler and was having large bubbles in the fuel line and engine would have to be set way rich in level attitude to keep running in nose up or positions. I removed the tank and looked for leaks in silicone or brass tubing and rubber seals and replaced all tubing with fresh tubing . Don't think there were any leaks. I sealed the exhaust tube closest to the exhaust completely leaving the farthest one open but with a silicone tube brass tube nozzle on it ( I had one tube nearly blocked previously to increase muffler pressure). I checked the carb to engine o-ring seal and snugged it down. I probed the fuel inlet nossle and took out needle valve and probed with fine wire and blew orifices out. I noticed that the screws I had used to attach the hose clamp pieces to the muffler had come loose and were maybe leaking some precious muffler pressure. I also noticed that the screws that hold the two halves of the muffler together were a little loose. The exhaust outlet tubes were able to turn in the muffler casting and were also leaking some air. I sealed all the screws in their holes, the exhaust tube holes and the muffler to engine exhaust joint with Permatex orange silicone hitemp sealer. I drilled out the rather small muffler pressure fitting.The old Tatone Pitts muffler is a small unit and has two large exhaust outlets one of which must be blocked completely and there must be no air leaks as muffler pressure is minimal and there is no baffling inside.One or more of the above fixes solved the large air bubbles in fuel line and tendency to lean out with nose up, as the thing starts easliy and runs great WOT in any position now. Hope this helps other frustrated Pitts muffler users. PS I added filters in the fuel line and muffler pressure lines while I was at it, making sure they did not leak air.