A friend of mine transplanted an 87 Mustang 5.0 H.O. and 5 speed transmission into a Ranger. All of the wiring for the engine and trans was transferred as well. The engine runs good when first started but after it warms up, goes into closed loop, idle speed surges and when driven, the engine hesitates and chugs at times, mostly at lower speeds. Not as bad at highway speeds. The only things on the engine that are not installed are the TAD, TAB and EGR solenoids, and the thermactor system. The EGR valve is installed but not hooked up to vacuum, although the electrical connector is hooked up. The engine is stock, no modifications done. KOEO codes include TAD, TAB and EGR codes. KOER codes, the first time I ran them had a code for TPS, I believe code 63. Tested TPS, has 5V ref and at idle is at .73VDC and increases with engine speed. The second time I ran KOER the TPS code was gone but a code 92 showed up. Tested the O2 sensors at the ECM, both seem to be working, neither one stuck high or low. I have no idea how this engine ran when it was still in the Mustang. Any help would be appreciated. Thanks.