here are the before and after readings from 150,000 miles on Main cat and gutted precats.
Also in regards to noise and drone. I have a custom 2.50 dual magnaflow with out resonator.
argh the drone was terrible. i loved it at first but geez the drone inside the cabin just made me hate it once you revved past 4500rpm.
i did find my PCV valve unplugged causing unmetered air to go into the engine. and i think this initially caused my O2 readings to be high and then the o2 sensors just dump more fuel in. but at any rate i fixed and retested with the new magnaflow cat and the readings got worse!! i drove the car from carlbad to LA and then smogged it, so this shows that the cat should have been hot enough to work well.
my engine does not burn oil, i performed the UIM and LIM cleaning before testing and everything was surprisingly clean! if you look at my readings they show that the engine is in good condition except that the cats are not doing their job. Also i have put new precats, and i have not felt it different other than it is quieter and the butt-o-meter is never wrong.
but hey if you feel like you gotta try it do it. heck i did.
i have a two bolt flange but need a three bolt. stazi said i could take the whole setup to an exhaust shop and have them mod my stock cat to work but i was kinda hoping to find something that would just pop in. 