I glanced at a pretty thorough e-mail that was fowarded through mopax (a mopar autocrossers listserv).
I'd say there are a lot of missing pieces in the hysteria.
#1 What scale is the test?
#2 According to CHP, the muffler test was for approving mufflers under a program no longer active.
See Questions 9 -11.
#3 CHP guidelines are basically common sense: See first part of
CHP Bulletin 98-100
Enforcement Guidelines
The only drivers who should be cited are those whose vehicles:
1) are not equipped with a muffler
2) clearly emit an offensive, harsh, excessive noise, or
3) have a clearly defective exhaust systems (holes, leaks, etc.)
Clearly the officer has some discretion, but its also clear the department is discouraging citations that can't be proven in court. They basically say the muffler test is impractical for law enforcement in traffic.
"Enforcement using Section 27150 or 27151 VC is usually more appropriate and effective."
My takeaway is Don't Panic.