Exhaust ticking
 

'00 Boxster non-S with Tip (55k miles)

the box has been ticking for some time.. sounds like it's at the driver's side right in front of the rear wheel, but I have not had it on a lift to thoroughly diagnose.
My indy has mentioned that I have a "minor" exhaust leak during my last oil change, but said it isn't dire to fix immediately. it has since started throwing an 1128 CEL code every several hundred miles of normal driving.

the ticking does not change volume, only speed of ticking changes with rpm change. when I'm in a drive-thru or next to a wall or fence, the sound echoes and is pretty loud.. makes my car sound "cheap"...

mechanic has suggested letting him smoke the exhaust system to find the leak, which I will have done after christmas.

any idea what I can expect to pay for this "smoking the sytem" and any other tests I should have him run after the leak is fixed?

side question: should a shop charge for diagnostic testing (pulling STFT and what not) when replacing a part or should this be part of the replacement price?