Often when my S hits V-tec, I hear a metallic clang. Is it possible that I can actually hear the cam lobes switching to V-tec? Or should I be worried?

 

if you have a model year 00 or 01.. this is referred to as the "buzzing noise" TSB.. i think it is TSB54 where they have to replace the clutch

 

I'm not sure what the VTEC issue is but it is very unlikely to have anything to do with TSB 054.

 

I agree... the buzzing noise in during decel around 3-4k rpm... when you say clanging noise to you mean a ringing noise near redline. Mine does this, but it is a high freq. noise from something in the car vibrating.

 

You're probably just hearing the crossover into VTEC. This noise is amplied with a cold air intake.