I'm going to install a set of hooker headers 2055 on my otherwise stock 5.7. Emissions police are not a problem. I would like to eliminate the dual cats, and just run staight back to the Magnaflow muffler. Will the decreased back pressure improve or hinder performance. I have been told that you need some back pressure, but I think less is better, Any comments?

 

Your hunch is correct. Back pressure is never good. You want as little as possible. The backpressure issues people refer to deal with the EGR valve. Your set-up sounds good but I would recomend a single high flow cat to replace the duals. They tend to tone the sound down a bit as well as refine it a tad. There is less chance of drone and rasp when you run a cat. You also keep the people driving behind you from gagging.

 

actually......

the backpressure myth comes from people seeing increased torque with smaller exhaust/header combinations.....

what they are seeing is not an increase in torque due to "backpressure" its from better scavenging.....if you open the exhaust up too much, with a poorly designed exhaust system the exhaust ports get lazy, and don't scavenge well (not enough velocity)

your exhaust should consist of a high quality header, as big as you want to go (if you don't need 2" primaries, it won't hurt, just wont help either)

basically, scavenging abilities held equal, the less restriction (backpressure) the more power

restriction ALWAYS causes a loss of power, any pressure is a result of a restriction

to clarify.....

you want maximum flow for maximum power, and header and collector quality will determine scavenging ability, which will further increase power.

anyone that says you need some backpressure is an idiot and doesn't know what they're talking about

 

And to clarify a bit more, this operates on the helmholtz theory of resonation. You can run as large a diameter tube as you want, but you will need to modify the length of the tubing to keep the header tuned. It's some pretty interesting stuff, same exact way intakes are tuned as well.