I thought I found a pretty solid setting on the KX450F after a few days building different fuel injection and timing settings via the hand-held Kawasaki computer along with the stock exhaust. I wanted more punch over stock and an engine that was a little more awake. When we installed the FMF with no insert/spark arrestor and with the ignition and fuel back to stock, boy did this bike come alive, almost too much. The pull and surge into the mid-range is instantly noticeable. I was never able to even come close to this change in power with FI/Ignition alone. I love this bike so far and the FMF just added more fun and ease to build power in an instant out of corners and on jump faces. The hit in the middle can be controlled via a steady hand, yet if you twist too hard the rear will break loose easier than stock. The jump between running the insert and no insert is very noticeable. I preferred the setup without the insert unless I was riding a very slick or extremely rough track. I almost wished for a between setting, a little less hit without the insert and a little more with the insert. I used the Kawasaki tuner to add a tiny bit of fuel and retarded the ignition 1-2 positions right as the bike hit. On some tracks this was enough to tame the hit just a hair and you could still ride aggressive and enjoy the prowess of the FMF with a smidge of the hit slowed down. If you are a power monger or a guy like me over 200lbs, the FMF is the key to making the 16 KX450F even more fun in my book.