Exhaust Gaskets

I've had my exhaust off a couple times and didn't install new gaskets. After reading through some threads I realize I need to go back and do that. Already ordered them from Z1 ent. Not sure if there are any leaks but I'm gonna replace them anyway. So, my questions are, 1. What Kind of problems would an exhaust leak cause? 2. If there is a leak wouldn't it be noticeable to the ear? Just gathering info here, Scott

you would hear it.

You will hear a loud "crak-crack-crack" sound when you open the throttle and loud pops when you let off.

and maybe a pffft sound at idle.