The UDP's reduce the amount of work the engines requires to rotate a little bit and frees up a few extra ponies, but in turn it lowers the output from the alternator. I think with a stock sound system it's ok, but with aftermarket amps it can be a problem. You would need to install a higher output alternator in order to make up the difference.
chevy runs deep, Don't step in chevy!
67 Coupe 289 - TCI C4 w/2k stall; Holley 4150 570cfm; Performer intake; mild cam; Pertronix HEI; 302 heads; Roller Tips; Hedman Tri-Y headers; H-pipe w/Flowmaster 40's; 9 in posi 3.50; 205/50-17F; 225/50-17R.