I bought a new 2019 zx6r Feb of 2020 and put a M4 slip on exhaust on in within the first month. Ever since I been having issues with the bike but there are work arounds so I didn't really worry too much about it. As of today the bike has about 2800 miles and the M4 was installed at about 300 miles. Now I figure I should probably look into these problems, so I figure I post here to get an idea. If bike is cold it will start no problem and there is zero hesitation. However once the bike warms up it will not turn back on (if shut off) without giving it a little gas as can be seen in the video. Also I wasn't able to replicate it in the video but eventually it will start hesitating if given very little throttle and sometimes even completely die, if you give it a little more (say 25%) it will hesitate but will not die. At higher RPM's say past 4k there is zero problem, even cruising around under 4k there is almost no problems but a couple of times the bike did sputter a bit cruising at lower RPMs. I'm thinking after removing the cat and adding the slip on it seems to be running really lean at low RPM's but I haven't heard much about other people complaining about issues like what I'm experiencing from just adding a slip on. I'm going to get my ecu flashed soon and hopefully the problem is solved. The bike also idles completely fine without any issue cold or warm it will idle fine, just an issue getting it started when the bike is warm.