In changing from stock exhaust cans to aftermarket, I noticed several things. Of course, when I closed the throttle and coasted in gear, the bike popped or back-fired regularly. I imagine that is because the cans leaned out the mixture. But, I also notice what I call more engine brake effect. With the aftermarket cans, I am being thrown forward (and I have to grip the tank) harder when I chop the throttle. Why? Does running lean increase the engine braking? If so, why?