i'm gonna be getting the S&S headers from l-tuned and i have a greddy pe cat-back exhaust. i was wondering what i should do from the header to the cat-back though. straight pipes? h-pipe? x-pipe? what do you recommend? what's best for performance/sound gains? thanks in advance!

 

Do you have a 300 or a 400/430?

It's not really clear to me whether a cross over pipe (H or X) is beneficial to an inline motor, but the bmw 335's come with a crossover pipe from the factory. A cross over pipe is definitely beneficial in a V motor... Iirc, h pipe delivers extra low end power while the X is for higher end power. I personally prefer the sound from an x pipe.

Also, please run some high flow cats! Straight pipes offer very minor gains over high flow cats. They do cost a bit more, but cleaner air is better for the environment as well as your own lungs.

 

i have a 400

 

Stock cats are high flow... keep them.

Stock Y pipe works well to 270rwhp/325 engine hp. No need to change anything at this time. Add the headers to your existing parts and enjoy.

 

i have 337rwhp though lol