The Thermactor air pump (smog pump) supplies air to the heads or catalytic converters. This air helps break down the excess HC (hydrocarbons) and CO (carbon monoxide). The air supplied to the catalytic converters helps create the catalytic reaction that changes the HC & CO into CO2 and water vapor. Catalytic converters on 5.0 Mustangs are designed to use the extra air provided by the smog pump. Without the extra air, the catalytic converters will clog and fail.
The Thermactor air pump draws air from an inlet filter in the front of the pump. The smog pump puts air into the heads when the engine is cold and then into the catalytic converters when it is warm. The Thermactor control valves serve to direct the flow. The first valve, TAB (Thermactor Air Bypass) or AM1 valve) either dumps air to the atmosphere or passes it on to the second valve. The second valve, TAD (Thermactor Air Diverter valve or AM2 valve) directs it to the heads or the catalytic converters. Check valves located after the TAB & TAD solenoids prevent hot exhaust gases from damaging the control valves or pump in case of a backfire. The air serves to help consume any unburned hydrocarbons by supplying extra oxygen to the catalytic process. The computer tells the Thermactor Air System to open the Bypass valve at WOT (wide open throttle) minimizing engine drag. This dumps the pump's output to the atmosphere, and reduces the parasitic drag caused by the smog pump to about 2-4 HP at WOT. The Bypass valve also opens during deceleration to reduce or prevent backfires.You will get these codes on a koer test when you bypass the smog pump.
(Code 44) RH side air not functioning.
(Code 94) LH side air not functioning.
These codes won't cause any driveability issues though.If you plan on bypassing the smog pump permanently and you don't have to worry about going through emissions testing in order to get your tags,you can remove the tad/tab valves and hoses,plug their vacuum hoses & cap the end of the crossover pipe.If the smog pump isn't functioning (due to being bypassed)those valves,hoses & crossover pipe aren't needed for anything.If you do have emissions testing as part of your registration requirement,you'll have to keep the smog system intact or it will never pass.It won't pass without converters either.I assume emissions testing isn't required in your county,otherwise you would still be running converters.Make sure you cap/plug all vacuum hoses that are part of the thermactor system, otherwise you'll cause a vacuum leak.You can plug the hoses that go to the tad/tab valves or remove their hoses from their vacuum solenoids (mounted to the pass side strut tower)then cap the vacuum solenoids instead.
Codes 44 & 94 won't cause the check engine
light to come on.If any codes are present which are related to the tad/tab vacuum solenoids(8x codes)they will cause the cel to come on,but you can install resistors in place which will turn the cel back off,but you shouldn't have any 8x codes present when deleting/bypassing other parts of the smog system.