Umm - in regards to sticking your head in the smoke - I would imagine it's probably not the healthiest thing to do, esp. with modern fuels and the additives - hehehe.
It's possible that if the engine has coked up a fair bit over the years that smoke could be slightly greyish or it could be rich mixture (like my car).
See if you can smell a *very* petrol-like smell near the rear of your car (although don't smell too hard) that would indicate an overly rich mixture. Oh, and yeah, do the bubble test, like, yesterday or something