Funny you should mention a Corrado VR6 there as I couldn't help but think back to mine as soon as I saw the talk about timing chains.
My previous car was a Corrado VR6 and they usually do sound fantastic, however, one day it made the worst sound I've ever had from a car and that was because the timing chain tensioner bolt lost oil pressure, the chain came loose, skipped teeth on the cam shafts and did a lot of damage! I had 8 bent valves, a damaged cylinder head, cylinder walls, piston rings and bottom end bearings! So yeah, it's worth getting any timing related belts or chains done if they're at all loose.
Having said that, usually loose chains sound like exactly that; a loose streaming metallic chain and not a regular tap / tick.
That video of the injectors is interesting and I would expect that is more the noise you're describing if you say it is like a diesel.