Thinking I might have one on my rear cylinder. What would be the tell tale signs?

 

Sorry to answer a question with a question, but what makes you think you have one?
Anyway, it could be a ragged exhaust note, uneven idle, low rpm surging, lots of decel popping and popping between shifts.
Check to see if the flange nuts are tight. If so, with the motor warmed and idling up try blowing cigar smoke or hold an incense stick at the flange and see if it gets blown around.

 

Look at the head where the pipe connects, it may be black or rub if it is black to see if there is any soot.
I use a piece of toilet paper on a long pliers. a small piece is all you need. If it is leaking the paper will move from the air.

 

You can fill it. Put you hand close. Not sure why anyone would think it would cause popping. Air is coming out, not being drawn in.

 

Some decel popping yes, not sure if that is related to a possible leak or tune. Idle is good and even, no surging, exhaust note is even, and no popping between shifts. Thought I felt air on my hand near the rear port, but couldn't be sure if it was just from heat (cold day). I'll try the smoke. So I should see no air disturbance?