I was in bonanza (only 300 hours on the engine) yesterday in IMC, and the engine started running a little rough. After a while, the roughness turned into a jolting miss. The engine was missing and it was becoming more frequent as the flight went on. I Lean the airplane for 25 rich of peak in every phase of flight, so i don't think i fouled it by running it too rich. Has anyone has problems with their engine missing before? any ideas? Maybe it's not even a miss. Maybe it's detonation or something.