The Pro Circuit T-4 complete exhuast has been the best pipe for my best friends z-400 he has tried the yoshi and wasnt happy with it at all kept making a popping noise when we let off the throttle at half throttle or more thought i was lean but we know it wasn't, then we tried the the Sparks pipe and it just didn't seem to give it the "Boost" we were looking for. We ended up with the T-4 complete system and it run very hard were running the jett size a lil less then what we should be but like i always say "THE LEANER THE MEANER"
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