Originally Posted by Werks

Ok, just pull the engine apart and see if you see anything. I honestly don't think the motor is the issue though because if it was it would not run fine for 5 minutes and then start acting strange (unless it was too lean but it sounds like you took care of that concern). The issue that you are describing sounds like it might be a pressure issues, replace the tank as you mentioned and change the fuel line at the same time. Let me know what you come up with!