You won't "need" a tune, but you will see no benefit from it if you don't; down pipe will added only 5-10 hp with a proper tune for it. I would get an intercooler also and then get a custom tune.So I'm new to tuning and bolt on mods... I know that some things do not require a tune. My car is mostly stock. I have green filter, and resonator delete. I'm looking at getting a CFM catless DP but I didn't know if I HAD to tune the car to run it that way? I appreciate your guys help and (hopefully) not flaming me over a simple question. Thanks guys!