Here's a odd one. when I was testing the repair on the thermostat housing tonight for leaks (finally got it fixed) I had it idling in the street. When the steering was turned to the maximum both ways (in park) it caused the engine to bog down and pickup again. Any idea what is going on here?

93 F150 with the 5.0 V8 and a automatic transmission

 

Your P/S switch is either disconnected or bad. It's just above the steering box, two wires. Signals for RPM increase, when P/S pump is active.