or would it be wise to by a MSD cap? Does anyone know what's so special about MSD's"PRO CAP?"

MSD Ignition doesn't specify one for the H22. Will MSD distributor cap part#8291 work?

 

Your factory cap is more than up to the task. The MSD cap was originally designed so that vehicles with internal coils can utilize an external coil, an easy bolt-on mod. On my old D16 I simply used a factory prelude cap when I added a coil. What's so special about the Pro-Cap?......nothing, except for the fact that it grabs attention reading "MSD" on it. Waste of money.