You will definitely feel gains from the header, and you will probably hear more exhaust noise from under the hood, rather than out the back tailpipe...I drove with the OBX - MAM High-flow cat and the stock axle-back for a while...and loved the quiet power. I only upgraded the axle-back to the MSP Racing beat and definitely thought it freed up the flow. If you can get a cheap axle-back, I'd say for the money it's better than a full cat-back...The stock diameter is 2.25" and the Racing Beat full Cat-back is only like 2.35", so most of the difference is in the muffler can itself...Anyway, I got my exhaust for $60 bucks, so I all about the deal. No plans to upgrade in my future, you'll only get like 1-2hp out of it anyway, so why spend hundreds of bucks.