The T6 s have been a good pipes for me and I have only ridden the T 5 s for a short time but I think I'm gonna like them to .From everything I have read and researched about the two pipes T5 or T6 is that the T6 are a better low end pipe and good for stock bike with bolt ons and the T5 s are better for porting and mods and a top end pipe .Although I will say these T6s with pod filters , +4 timing plate, cool head, and v force 4 s perform pretty darn well for a stock engine and makes for a reliable fun ride.