I have an intermittant problem between 3 & 4 thousand rpm's.
The motor falls flat on it's face, Like it's running out of gas.
When I back off or up shift it takes off till I hit that rpm again.
I have changed fuel pump, fuel filter, egr valve, plugs, wires, coils,pcv valve.air filter, exhaust. cat changed in 04, fuel pressure regulater,oil,oil filter,coolant,gas cap, & thermostat, any ideas?

just a thought , no positive , but im thinking perhaps the coil packs? maybe getting a weak\insufficent spark at higher RPM's? i would investigate further into it before going out and buying new ones , cuz im not all that positive , but hey , some half assed advice is better then none eh?