I looked into exhaust mods in CA 12 years ago, and other than louder mufflers there's no point. I'm stuck with low flow cats and small diameter pipe. If you can come up with something that gives a heavier sound and adds any HP at all, and is still CA legal I'm all ears.
Whatever I installed would have to unbolted and the stock pipes put back on every other year. I installed delete tips from Wes at Innovative Interceptors and left it as is; that did give a healthier sound, but not like some of the new mustangs I hear around here these days.
2003 black pre-decontented 300B #5886 of 7838; Born on 10/31/02
MartyO tune, 4:10's, T/A stud & girdle, MMX shaft+DS loop, Metco control arms, Quickor RSB, Addco FSB, Megs delete tips, Granatelli solid coil connectors, NGK plugs & LP 170 stat, DR rear engine cooling mod, PI 3000 TC, Level II tranny, Art Carr deep pan, Steeda pullies/billet caps, billet door locks, Ford Racing oil cap / polished coil covers, PHP CAK & Metco carbon fiber intake, DG Motorsports CF radiator cover, Fumoto oil drain valve, oil deflector, real Autometer gauges, ScanGauge II, Weatherflectors, underbody lighting kit, Zack chrome grill, OEM spoiler & door edge guards, KB dead pedal, Dynopro aluminum sills & pedals, Viper alarm w/ remote start, MM fender badges, red painted calipers, SS inserts, Silverstar Ultras, hood bumpers, 35% tints, Gorilla lug nuts, MM valve caps, Pro-Guard, DD trunk lid liner, CM UHI kit, CM Godshead rear & steering wheel badges, S-55 badge, FilterMag, MM trunk bib, ported sub-woofer.