Is the noise filter you put in like this?
cause I know alternators can cause noise.
The Crutchfield ad also says FWIW,
"Sometimes alternator whine can be cured just by topping off the fluid in your battery or properly grounding your in-dash stereo."
Loud pipes save lives.
1973 GTV - bought 3/06, intend to keep forever
1969 GTV, #AR1530021 - sold 10/72, guess didn't intend to keep forever
Current project: '69 Corvette bought in '73, DD '73 - '80, in storage 1989-2002, now apart