Will adding an X pipe or anything else add a little more hp then just straight piping the car with 2.25 piping?

 

Are we talkin SC400 or SC300? That'll help us out! Either way small straight pipes won't make great power and will sound bad. On the V8 - a true X-pipe with 2.5" piping, resonator(s), and nice straight through muffler(s) will sound and perform the best.