Here in Oz, removing a cat could cost $10,000
.
Cats with the guts knocked out of them tend to flow badly aswell. A decent increase in volume/cross sectional area causes a build up of pressure (resistance to flow).
Some time this isn't as bad as a poor flowing cat, but if the standard cat (in decent condition) isn't providing enough flow restriction to reduce performance, it's a fare bet that a gutted cat will.
__________________
Don't worry what other people think, they don't do it very often.
Alfa 75 Potenziata, Twincharged AW11 MR2, RB20DET S13 Silvia