Hey all,

I have an 06 lly that is stock at the moment. I plan on adding a programmer to the truck to increase performance ,mileage, and towability. I don't plan on any huge increases probably 60-90hp. Would just replacing the stock muffler with an aftermarket freeflowing one make much difference? I don't really want to mess with the cat just yet. Would I just be waisting money? Any opinions would be greatly appreciated.

You can always buy a cat-back for now then get the down pipe later so that when you have to take you truck in for service/emissions you can put the cat back on.

You will gain a few horsepower. You will probably notice some difference in power (or fuel mileage if you drive it easy.)

You will lower the exhaust gas temps, which is better for the engine, and almost a must for towing.

In the long run it will pay for itself. In the mean time, you'll enjoy it. I bought an MBRP system from a vendor on this site, and I love it!

I was concerned about the same things you are, Bainer. I put the MBRP 4" cat-back system on last year. I did gain a little relief in the EGT's while towing. I didn't want to mess with the cat either. But the cat is the restrictive part of the exhaust and after a year with this system, I've decided to add the downpipe. You didn't say whether you were going to upgrade the exhaust. I'm not sure just replacing the muffler will gain much. The 4" pipes are a part of the equation.

BAINER 4" Duals and ditch the cat, we'll do it in the parking lot at work:D

Going with a turbo back 4" system is a good idea. You'll love the sound, you'll increase the efficency of the motor, and get better throttle response. Also when going with a programer the extra fuel will increase your egt's so the exhaust will help there aswell..