There is a welded on stainless steel screen spark suppressor insert in the end of the can that you can remove for absolute straight through exhaust. Plan on keeping that insert installed as without it, it is EXTREMELY LOUD as it breaks up the sound wave pulses to keep it from sounding like a straight pipe.
I measured with a decibel meter three feet from the straight through exhaust and it hit 105 db - this is NOT GOOD for your ear drums!
With the stock YOSH spark suppressor in its stock position, it measures 98 db at three feet.
Stock muffler exhaust was 88 db at three feet for comparison....
With two balled up 4"X4" stainless steel screen inserts crammed into the pipe and then installed the stock spark suppressor to keep everything from flying out, it measures 95 db at three feet. This is acceptable to me as idle is nice and throaty, cruising with no load is nice and throaty, and stepping on the gas is still pretty loud when you want max power and acceleration.
It does start, idle, and run magnificent! Probably another 5-6hp with K&N and Yosh pipe over stock setup!
Plus, when you turn it off -> there is no tingling of the header pipe cooling down. When you turn it off there is no sound at all, this is a nice improvement over the OEM stock pipe and heat shields tingling for five minutes during cool down. I did not put the OEM heat shields back on the header pipe, I just wrapped that with thermal header wrap to keep the heat radiation minimized and increase heat flow out the muffler.