I keep hearing so many opinions both for and against the theory that using a cat that is half an inch bigger than the rest of the exhaust system will be beneficial.

Many people argue that the smaller sections of the exhaust will become the bottleneck and render the extra diameter inaffectual.

Other people claim that the flow through even a high flow cat is more restricted than the rest of the exhaust and so making it a little larger evens out the flow rate more.

Can someone set me straight please!?

 

i prefer to be an open header type of guy, lol no need to worry about restrictions, lol jk well u can settle fact or fiction by dyno testing different therorys, depending on setups, mandral bent exhuast usually dont have a restriction problem because its the same diameter all the way through, but im not sure about the cat issue