Guys, just reading your thred,I fit exhaust for a living and if you knock the guts out of a cat it is the best way of making your car sound like a shitty 253 kingswood. Although they flow well the gutted chamber becomes a resinating peace of crap.Just fork out and buy the cat should cost no more than $300 fitted.If in dought about power loss do a back to back dyno on straight pipe v's high flow cat you will be surprised!