Overheard some discussion at Mosport that by reving up the engine smoothly and letting it back to idle gently, rather than cracking it up and down, the reading was several dB lower.

Hi Jim, for sure, bring revs up to the specified rpm smoothly. If you end up below the necessary rpm just repeat the process. Some get in trouble by reving quickly and exceeding the required rpm for the test. Even going slightly over the required rpm can really make for a jump in the noise reading. Regards, Dave