OK, old carb/mech pump/no reg=ran fine. new carb/elec pump/reg=acting up. I'm assuming what you said that the elec pump is adequate & I'm assuming it has a non restricted (~100 micron) filter before it. What about adj the reg for more psi? the most it would do is (possibly) flood it just for 1 test which ain't gonna kill ya & it might very well be the problem (& an easy fix). All that is left is the carb. Holler how it goes. PS It just crossed my mind, what other filters do you have & was it not there with the mech pump/no reg/old carb