You can gut the ones in your car in one afternoon. A long 1/2 drill bit, long chisel, hammer and a respirator. Back in 02 when the Subaru WRX came out, we all gutted the preturbo cat to get it to spool faster and because the facotry cat had a habbit of sending pieces of catalyst through the turbo, which is not a good thing.
I'll gut mine this weekend and let you know how it works out. If it's a success I'll post a DIY. If not I'll cry myself to sleep.
