[BLKMGK]

You shoudln't see pressure drop. In fact on my car I had so much fuel at idle I couldn't bypass enough of it. I now stage my pumps. I run two totally seperate lines to the front to my rail...

 

[BLKMGK]

One OEM pump draws about the same amperage as two Walbro however I've been told not to lower voltage on the Walbro pumps. Fuel pressure shouldn't be dropping unless the pumps are having trouble keeping up or the regulator isn't compensating for the lowered flow when hot. One thing I found on my regulator was that it leaked vac - BAD. The adjusting screw on top had to be sealed with Teflon goop to solve that. Make sure you aren't at either end of your adjustment range too. I trigger one Walbro with my fuel ECU to a relay and another through an output on my AEM.