This is Funny. Back in the 50s we used steel wool (Stuff it up the pipes) to quiet the "Glass Paks" we had on our Hot Rods. This was in NJ where state inspection was in STATE run facilities. We would drive to (near) the inspection site and then pull over and stuff steel wool into the tailpipes. Self tapping SS screws inserted crossways would keep the steel wool from blowing out too soon.
THEN: We would shut off the moter and PUSH the Hot Rod ..in increments up to the inspection building......In a line of cars waiting to be inspected.
.. Didn't want to Burn Out the steel wool before we got there.
It always worked.
I suspect the Officials saw us coming with our Hot Rod ..and looked the other way. We were never questioned. The last time I remember, the steel wool was melting down and puffing out of the tailpipes even as we were exiting the facility with our Sticker.
NB