The continuing saga of my 4*60 and bubbles in the fuel line.

I can't think of anything else to do. So far I've done the following to try to remedy this problem:

1.) Yanked out the old fuel tank, replaced with new tank and new lines
2.) New foam around the tank
3.) Installed a fuel filter
4.) Balanced prop.
5.) Rechecked engine mount and tightened up all hardware


I'm still getting bubbles....and I've no clue what to do from here. Any suggestions? This thing is driving me crazy.

BTW I'm running a Saito 100 just in case that matters.