Thanks to everyone who responded to my plea for help. Thinking it was
the muffler, I took it into my local shop. He says:

1) There were some loose bolts on the exhaust manifold that he tightened

and

2) I have a stuck lifter which is causing a tapping noise. He says to
fix it I should change the oil and add some Slick 50, then let the motor
run for a while revving it occasionally until it gets unstuck. He says
this might take up to 45 minutes.

Does this sound right?

Scott Semyan
'85 Westie
Seattle, WA