how does a high flow sports cat work. Wot bhp do u gain. Could i fit one after i had my exhaust fitted or would i have to get it all dun at once. Cheers
A high flow cat does just that - high flow - it lets the fumes flow out better.
Bigger bore and the better insides to allow more flow.
You can get it fittted at the same time or after - tho i would get it done at the same time if you can afford it!!

You can get 10 - 15 bhp more

Quote from milltek " A Milltek Sport Hi-flow Sports Cat which will be fully integrated into a large bore downpipe, has only 100-200 cpsi depending on application. These cats have an open area of between 75-85%, thus reducing back pressure substantially and increasing flow rates, all very desirable for extracting more performance, especially on turbocharged engines. Emission levels are maintained at legal limits by careful selection of the volume of the metallic substrate. Lamda probe positions remain unchanged from the original equipment. "