2003 Fatboy 88 c.i. Engine misses and lurches when at or near lugging speed while driving at a steady speed. Ok when accellerating or when engine under load or driving fast. This only occurs when gas tank is half full or less, problem disappears when tank is filled. Problem probably is fuel pump, filter, regulator or leaking hose. Looking for advice before I open it up. What confuses me is why this only happens at lower speeds and not at higher speeds when fuel demand should be greater.

 

Fuel demand is the same at all times... The pump is running a constant pressure of 55-65 psi at all times...

More than likely, you have a fuel line with a hole in it....