Got a Tomos A35, mid nineties and I am using a BiTurbo muffler system. I had noticed a big change since I had first installed the kit, at that time, it would get to 30 in about five seconds, and now it takes a lot longer to get that fast. Also during that time, I had a case where my BOSCH Platium Spark Plug had fouled. I'm guessing the plug caused it to produce excessive carbon to bridge the exhaust port. Is that what happened? Is there another way to restore the acceleration either than decarbonizing the exhaust port, or is that all I need to do?