Rode today and my 426 was poping on deacceleration. Well it got louder and louder. I came off the track and grabbed a handfull of throttle and when I let go with each pop flames came out of the exhaust. A bit of background.... I got the 426 which had a stock header and an Arrow pipe. I managed to get hold of a ProCircuit setup, header and a couple of pipes from H4B. I ran the PC header and the shorter of the pipes for the last year. The PC setup gave more bottom end and better throttle response. A couple of weeks ago I was racing at Canada Heights and decided that I would run the longer pipe. Well I had it sound checked and it was registered at 102db. This pipe is quiter than the shorter pipe. It also gives less power at the bottom end. Anyway I thought I would do my bit for the noise problems, so I put the stock header and Arrow pipe back on. This is alot quieter but unfortunately not as powerfull. I used to run Optimax in the bike but recently I have run on normal pump gas. My son said his bikes runs better on Optimax so this weekend I switched back. So the difference between this weekend and the last time I rode was the stock header, Arrow pipe and running Optimax. What could cause these flames. It did look good though. Some kid said he wished his bike did that. I said I wished it didn't.