My truck is stock w/ 185k miles on it. A few weeks ago, it developed a stumble around 2500 rpm in all gears. I replaced the plugs, air and fuel filter,and borrowed a known good maf, all to no avail. The fuel pressure is good, according to the procedure in the Haynes manual. I cleaned the throttle body and the MAF as well. Once I disconnected the EGR valve, the problem seemingly went away. Yesterday, I replaced the EGR valve and it's doing the same thing again.

Anybody run into this before? I'm pretty well baffled...