I was having some other problems with my truck about a year ago and I thought it could be the fuel pump cutting out.
The mechanic told me that these electric fuel pumps don't cut out or slowly decline in performance; they just quit working one day.
According to that guy's philosophy, the problem wouldn't be the pump.
But, if you ask me, it kind of sounds like maybe you should have someone check out your fuel pressure and make sure that pump's not failing.

Could a vacuum leak cause that? I've been surprised in the past by how much a vacuum leak can fudge up my truck's performance!

'99 Tacoma Xtra cab V6 TRD
TRD Supercharged, URD 7th injector and 2.2" pulley, 32X11.5 BFG All-Terrains, OME 881 3-inch lift/Toytec AAL, 5100 Series Bilsteins all around, and ProComp 130 lights.
No I'm not some creepy naked guy...