I bought a used 13' raptor. Only has a catback. It had some sorta tune (no tuner box came with the truck), and would not pass smog. for 3,500 miles the 02S. HO2S, and cat monitor wouldn't run. (in califiornia you can only have the evap monitor not ready) I read on here from others that the tune actually caused it to shut down some of the systems in the computer It shifted hard under heavy acceleration (slamed into gears), when youde come up to a red light and slow down the engine would like rev match, and the throttle kinda blipped between each gear. Engine sounded louder too The only to fix it was have someone with a factory ford scanner/programmer flash the PCU back to stock. Afterwards it was stock flash the shifting was much smoother under heavy throttle, engine quieted down (I have a magnaflow, and now its actually really quiet) you cant feel it downshifting either when coming to a stop. I dunno what kinda crappy tune it had. Who are the good safe tunes that don't F with the smog devices (sensors ect), but will gain some of that power back?