Not a Ford nut by any stretch, but I have quite a bit of experience with working on them! What's the fuel pressure under load? That is MUCH more important than the static pressure at key on, and idle. Tape the gauge to the windshield, take it down the road and floor it. The pressure should be pretty close to the key on engine off spec, since this would be a low manifold vacuum situation. Fuel volume is important as well, but MOST of the time, if it's able to maintain pressure under a load, it has enough volume. EGR should probably be commanded open pretty far at that point anyway, so that's not very likely the problem. Is it misfiring when this happens? Also, even though the catalytic converter is gone, the muffler can have stuff come loose and cause a restriction. I'll keep this one in the back of my mind, and if I think of anything else, I'll post it.