Ok so i mostly do gm and ford tuning, had a customer delete his catalytic converter etc for offroad use only. After licensing the PCM, going in and literally only unchecking the codes related in the engine diagnostic tab, loaded the tune, cycle the key and it will start and die with red security light flashing(skim error code). retune, clicked the option to unlearn skim. nothing. Reloaded the original tune i pulled from the vehicle..Boom starts and runs fine, reload my tune, dead in the waters...any ideas on what the hell is going on? verified with my scan tool the pcm still has factory vin etc after tune. like i said i made sure to ONLY change the 420 430 and O2 response codes on the tune to see what happened.. ANY HELP WOULD BE GREATLY appreciated. (also i searched my ass for this so if i missed it sorry )