Spura, good luck getting that motor figured out! Please post if you do. I finally retired my GO this weekend after it let me down AGAIN! I had the same problems you described, put on two new tanks, replaced pressure and fuel lines multiple times, put on NOVA carb. Mine only has 3 gallons on it and it has NEVER been consistant. I thought I would save $$$ and buy a GO, by the time I replaced all the parts, DNF's, I should have stuck with the NOVA's.
Just so you know I have been racing 1/8 nitro buggy for years and have never had a motor frustrate me so badly. Good luck with yours and let us know if you get it fixed.