Hello,
I own a 98 zx9r. Completely stock, stock air filter, no jet kit, but recently have added an M4 bolt on exhaust (no headers). The exhaust came from an internet source through ebay and in the informational portion it claims no rejetting/remapping is required. I plan to rejet the bike with a stage1 kit in this winter. Should i seriously consider any negative effects such as runningtoo lean or too rich if i don't rejet in the near futureand wait until the season ends like I plan to do? The instructions dont say whether or not rejetting is required and i havent called the companyM4yet. I would like to know what other riders would do before I jump the gun and get paranoid everytime I start my bike to go for a ride.

Thank you,
Jim (ZX9R owner)

 

Well seems to runjust fine.I seeno1 wants to give me any advice from their past experience. Jealous? Maybe it's because I'm too blind to see the obvious answer here.
I'll search for the best place to order a jet kit and be donewith this. If anyone has a good website don't hesitate to drop a line or two.
Thanks

 

Its recommended for peak performance, so no you dont too, but suggested for the future to let that bad boy out. Good luck to you.