Is there a similar issue with the DW 400 as far as heat?I have the ECUGN and a flex fuel sensor.
If your gas tune is on point, the flex fuel just works once you enable it.
One drawback I've had to deal with is with such a large pump (I have a RaceTronix 450LPH unit): if you're not beating the snot out of it, the pump puts a lot of heat into the fuel. Pumping 450LPH when most of it goes through the regulator back to the tank creates a bunch of heat from friction. I'll see fuel temps in the 140s sitting in traffic.
I have a PWM controller on the shelf ready to go in. It'll de-rate the pump by ~40% when the MAP is below 100KPA and should dramatically improve that aspect.