The reason I'm asking is I still have the tank pressurisation issue I raised here a while back but have still not got to the bottom if it. I talked with the factory and they suggest the issue could be the check valves are installed vertically and need to be re positioned horizontally (or vice versa, I cant remember what they said till I check) as they work better in one position as compared to the other. Another thing that has got me bothered is my previous Maule an M7 had the airspace between both mains connected, my M4 doesnt, this plane was 1 of 12 build in 2007 as a 50 year celebration of the original M4 . Maule has decided to put the this M4 back into production for 2017 but the FAA have mandated a connector pipe between the mains that my "limited edition" doesn't have. I wonder why the pipe was mandated. My old fuel system mains and aux (with xfer pumps to move fuel from the aux to mains) on the M7 was very predictable, alternating between left and right every 30 minutes with expected associated drops in quantity indicators, with the M4 it bizarre even when Im running on the left it seems to pull from both. Something aint right