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MAP sensor high indicates the ecm is reading high voltage on the MAP signal line during specific operating conditions. For default configuration, here's the code definition:
33 MAP sensor signal voltage was too high (low vacuum) for 1 second when throttle opening was under 20% and engine speed was above 1250 RPM.

You should be able to see MAP voltage on the scantool in key on / engine off condition to compare the reading obtained at the PCM wiring harness connector using a DVOM. Additionally, you can create simple resistor networks to connect between 5V, signal, and ground to create a "between" voltage to send to the pcm.

In a stock wiring harness the 5V circuit and GND circuit for MAP are shared with the EGR valve. Any issue which can cause a short to 12V on GND or 5V REF or an open on the ground circuit will also raise voltage on the signal line as seen by the ECM. To catch this on the DVOM you should be measuring voltage between the sensor ground and the sensor signal line.

Since the engine reacts badly while wiggling the harness, I would likely try connecting the laptop to watch ALDL data then taking hold of the harness and performing a Ford "Wiggle Test." Watch for significant changes in MAP or another sensor reading on the laptop.

I have had troubles years ago with intermittent code 33 on TBI equipped 1995 vans. In one case I found a broken wire in the harness causing an intermittent open. It was only apparent when the engine was very warm. In another case an aftermarket EGR valve caused an issue. In both cases it was frustrating to find because there were no symptoms showing while the van was in the shop.

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