I removed my muffler to see how fast it would go, but it went the same. I noticed something else that I think may indicate something, but I do not know what. As I would run the engine, I would hear pops at a regular interval, I know this is normal, I think it is it firing. Then as I accelerated the interval would decrease, the finally, when reach the top speed the poping would suddenly double in speed. Does this indicate anything? Thanks!