An '89 doesn't actually have a sensor for EGR flow, so code 33 really means the EVP or EVR circuits are showing a fault. Haynes shows exactly how to test them, and the TPS using a cheap multimeter. Older TPSs were adjustable, but before attempting that, you should make sure the throttle stop screw has NOT been. Read the links I posted in this thread:
setting the idle on a 92 bronco