The high pitched sound is like the Demolition Derby of young fire department drivers driving no-exhaust junkyard "Rice Burners" full throttle at the Galax, Virginia fairgrounds. Don't laugh. It brings in a crowd of young folk and the money is used to buy needed equipment for the fire department.

"Adding CFM to a truck will only help at engine speeds you don't want to use."
"I found there was nothing to gain beyond 400 CFM."