[s-cars] a new noise from Dave's car

[Dave Burig]

My friends,
I'm hearing a hollow knocking sound coming from under the car, in front of
the firewall.  Sorry, that's as close as I can isolate it get while it's
single digit cold outside.
Kinda sounds like someone on the inside of a coffin smacking the side with a
deadblow hammer.
The knocking is vehicle speed dependant, frequency sort of mimics the
baseball-card-in-the-bicycle-spokes trick, but with a 6-spoke wheel.
Hear it only while under load, not when coasting.
'93, non-CRB 6-speed, ECS stage 2
Any suggestions?
Dave B
Columbus, Ohio