no. who told you it's a must? they were wrong.yes.
any changes to the stock exhaust will result in backfiring.
Made by a guy on r6 forum. Cheapest that I've found. Good quality
Get em dub!!!um, its called experience and an understanding of air/ fuel ratios. 15 years certified automotive experience and almost 20 years on a bike
It's not a MUST for the bike to run, it's not even a must to reduce backfiring BUT
If he wants to STOP the back firing he needs to eliminate the fresh air charge. It can be tuned out to a certain extent (usually by causing the engine to run too lean) but will not be eliminated without removing the air injection system. pockets of air mix with unburned fuel in the exhaust resulting in an explosion..backfiring. By reducing the oxygen level ,post combustion, you greatly reduce the chance of backfiring on decel or hard accel.