Long list ?

First is simmilar to Reub-revhead, just had new exhaust fitted (2 into one 1 dogs) but now get a backfire when backing off, inlet leak and just coincidental that it has started now?
Second is with fuel tank design, now that the new exhaust is on, the fuel tank dosn't fit anymore, so I am getting a new one knocked up, as the top of the tank is above the filler level, can I form a reserve tank at the top of the new tank and set up some sort of pump system to pump the fuel up to the top tank, reversing the flow when the main tank gets low?
Third is re a tow bar. As I have no bumper bar ( f/glass Kalita) I reckon I can manufacture a bar that will fit onto the large bolts that bolt the engine mounts to the "chasis" then continue forward to the small brackets that are already on the "horns" in front of the box the bar would be extended from the large bolts mentioned before back to the tow ball end, reckon this would give a sorta canterlever efect. The trailer is a very light one (sort that the bikers tow behind their bikes) so the load would not be great. Whata ya reckon?
Thanks in advance
Don