[red82gt]

The mass air mustangs lengthen the pulse width to add more fuel to match the air coming in, the fuel pressure stays constant.

I'm not sure, but I think the SD computer can still control pulse width for part throttle from the O2 sensors and add a correction to the fuel tables. Upping your fuel pressure will add more fuel at WOT but you may not need it at your altitude. Remember, these things do run quite rich from the factory as a safety net.