And the answer is: a deposit of sludge...or something else...... was clogging the vent line...as I had no lift to get under and trace it.....I disconnected the line from the charcoal cannister....introduced as much solvent as I could (gas treatment). I didn't take much...I left it for a couple of hours and then, using about 40 PSI...I attempted to blow it clear....was feeling defeated BUT on my 12th attempt...Bingo...a loud pop from the gas tank (gas cap open of course) and the sound of air passing through the line and into the tank without restriction. Now I will add gas treatment into tank in attempt to break up any sludge deposits........as always...im elated when a TR6 problem is behind me......thanks for suggestions!