I'd check these things

- accelerator pedal travel (does it go all the way down)
- throttle cable (with a friend in the drivers seat pushing the pedal watch the throttle cable travel where it is attached to the throttle body...remove the intake to the TB and check to see if the throttle plate goes to wide open throttle
- if they are fine then i'd recheck all the vacuum lines including checking the connections for corrosion that could cause a leak on an otherwise good looking vacuum line
- you never said what ecu you are running nor said if there are any codes being thrown

one thing i always do when i'm stumped is call the dealer and ask to speak with a technician if the normal service representative can't help...i've diagnosed two simple problems from that method for free

good luck