I recently bought a 2004 manual trans 400 4x4.
What pipes do they make and what is the best jet kit for it or is there any other mods that might benifit the bike??
Thanks...

 

Your best bet for 400 go fast items is Speedwerx

 

Make sure you have around 1000miles on the engine so that it is good and broke in and you may notice more of an improvement from your modifications.

I think if I wanted to mod my 400 I would probably put a new muffler on, re-jet the carb and put a high flow air filter on like K&N. However, I currently do not feel the need to change stock for me other than new tires.

SJ