It is just a good idea to remove the wire at the coil, then test run. A bare/thin spot anywhere in the wire can cause arc-ing to ground to nearby metal, and cause rough running. The head gasket should be replaced, as it has lost some material from the first removal, and may not last long.
The head gasket on these l-heads is not as critical as on OHV models, so it is not likely your problem at this time.
I once worked on a small pressure washer that ran like crap, and a new coil was the only cure.
But I always take the time to make sure what the problem is before buying any parts, and suggesting others to do so.
So, while you have it apart, replace the head gasket.