You had me goin' for a minute there. I haven't had air for so long on my 2.6T that I forgot how the tensioner was set up.

Why not drill it out and tap for the next larger bolt? And use anti-seize this time...

Was the smoke still puffing, or a steady stream with the hood open and engine running? Continuing puffs might be the oil feed hose or coolant hoses leaking...

Not responsible for advice not taken...