Number 4 is the favourite cylinder to wear cam lobes, apparently because of design faults on CVH heads.

I seriously do believe all the high revving is what kills the cams so quick, i ragged the shit out of my cabriolet one day and the cam went, yet the cam in my Orion which i use daily is still the original and is in a pretty fair state, 114k miles aswell! But it doesnt go anywhere near the rev limiter like the cabriolet did.......