Post Master General
Join Date: Apr 2012
Location: Bowling Green, VA
I Ride: '09 ZX6R
Most if not all car FI systems use an oxygen sensor to monitor the exhaust gasses to maintain the leanest, safe fuel/air ratio. The ECU constantly changes the mixture based on the amount of unburnt fuel. Very few bikes in the US do this.
Because of this, reducing the restrictions in the exhaust can make the bike more lean. As long as the cat is in place, you are not affecting the ratio enough for that to matter. Once the cat is out, a remapped ECU is advisable.
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