here is the back story I have a 1988 Mustang GT 5speed hatch, I have done a complete EGR delete bypassing the coolant putting in just a delete spacer added a phenolic spacer so that the throttle linkage still worked, Converted to Mass Air calibrated for 24lb injectors, upgraded to 24lb injectors, 70MM throttle body, Cold air intake, Under drive pulleys, all new plugs wires cap rotor and ignition coil. On the test drive from converting to Mass Air I could smell the engine getting hot (temp gauge was not working, currently changed out the sensor) I pulled over shut it off to check things out. as I looked and felt around I noticed that the Upper Plenum was very hot like so hot that couldn't leave your hand on it. at this point I found no coolant flow I removed the thermostat and did another test I let the car idle and again the Upper Plenum gets hot quick nothing else does I can put my hand on the lower intake between injectors and its not that hot neither is the water pump, Valve covers. After shut down I could put my hands on the headers before I could the Upper Plenum. so my question is why would the Upper Plenum get that hot without exhaust running through it? The cold air pipes are not warm it doesn't start getting warm until the delete spacer.