Trying to find cause of engine roughness

[Harry_The_Pilot_Guy]

Hey guys,

I just had a flight where I got a few misfires while up at cruise.
Conditions: 23"MP, 2100RPM, 7500ft, cruise flight. I believe outside air temp was about 60°F
The engine misfired once, then again about 20 minutes later. The second time being more severe. After each time it misfired I did the following:
-Switched tanks (I had both mains selected, then switched to either right or left main, then back to both)
-Used carb heat (no additional roughness)
-Tried switching to the right/left mag
-Checked fuel pressure and turned on the elec fuel pump (no change in fuel pressure, so engine driven pump should be working normally)
-Checked oil pressure
-Checked EGTs, did not have a cold cylinder from what I could tell
The second time the engine misfired, I tried readjusting the mixture. I had already set it 50° rich of peak, but did it again to be sure. The mixture was slightly off, but not enough to cause engine roughness.
On the ground I inspected the engine on the tablet and everything was in perfect shape! Engine only has 9 hours on it. What gives?? I sumped the tanks before the flight and got 2 cups of water out of the mains. Maybe water in the fuel?