Haywood, 178=3lb boost 181=5lb boost and 185=7lb boost. 185 will require ECU remap and puts the ECU outside of it capabilities in stock form. 178/181 will run within ECU capability and you can reprogram ECU at a later time for optimum HP/TQ. You can still run the 185 it's just that the ECU will start to retard timing to correct for that much additional air. I hope that made sense.