Will I notice a gain in power or sound by switching to a high flow cat, and if so who makes a good high flow cat?

 

I don't know maybe 1, 2 hp??? Magnaflow makes a good high flow cat.

 

If the car still has the stock cat you should. I think you will notice it being louder than faster though.

 

I am using the Magnaflow direct fit catalytic converter. I didn't notice it get any louder or faster after replacing it, but it did pass emissions, and it was a good price.

Before I changed it, the original cat was hollowed out because the catalyst was falling apart and rattling. When I changed it to a functional converter the car didn't get any slower as many people would have you believe.