Your problem may be a faulty signal from th eignition module (this is the RPM signal) It is carried in a COAX cable in the wiring harness and when the foam insulation in the coax 'biodegrades', the signal goes to ground. Take a careful look at the individual wires in the main wiring harnesses goin ginto the 'computer bay', checking the harnesses at the 'hot' locations in the engine bay.

The 4000-4500 RPM cut-out is the normal safety feature of the engine management system--not supposed to rev over that without car moving (need speed signals from the tranny and each wheel to go above that cutoff)