99denali runs bad 1/2 throttle help please

99 gmc yukon denali has no power above 1/2 throttle under accel
bogs down everytime..
99000 miles
no check engine light
new cap, rotor, plugs, wires
new mass air flow
two new converters
all ecm values look good
fuel pressure good
was doing this before all these new parts, the problem is everything works under 1/2 throttle perfectly..
anyone respond

What is the fuel pressure when this occurs?

Also, have you checked exhaust back pressure?