Back to High Idle issue:

Per drawings, fuse for parking brake signal is good, relay for parking brake signal to high idle signal is good, the two items just mentioned (Parking brake switch and high idle switch) when activated, by pass the throttle petal and tell the ECM to increase RPM's, SO if the throttle petal works with out the high idle turned on it means the throttle signal is getting to the ECM. Not sure were to look from here.

Chuck