I used to have the Sparks X4 on my EX400. I switched to the Yoshimura because the X4 was way too loud for my likings. I did notice a little loss in performance, but well worth the sound decrease.

 

We have the LRD combo and we love it--------[img]i/expressions/face-icon-small-smile.gif[/img]

 

I've been doing lots of research on EX pipes lately(since im gonna get one soon), and the best pipes I have found are...

1. Hetrick Racing(X6 copy. cheaper, mo powuh)
2. HMF(1st choice for those that are price minded)
3. Sparks X6(MONEY!)
4. Yoshimura RS3(Nice)
5. Pro Circuit T4
6. CT Sonic

The list goes on, but I think I will either go with the Hetrick pipe, or the TC Shorty. I've done quite a bit of studying on this matter, so if you would like some more open opinions, "Ask, and ye shall recieve."