I have been thinking about having a Magnaflow muffler installed without a cat-back kit, just the muffler..would the correct size be 2.5 inches on this thing? The reason I would like to do this is to have a little more hp/tq for less downshifting out of overdrive going up hills, and the added sound would be ok too. I was thinking a 22 inch muffler because I would like it to be relatively quiet, something like a factory 2004 muffler sounds maybe. The guy I talked to at Sears said it wouldn't help at all with downshifting and I would probably lose gas mileage, is he correct about that? I also mentioned putting on a cold air intake and he said that wouldn't help either. I already placed an order on a cold air intake, and am planning on having a muffler installed soon. Any info. on this would be greatly appreciated.

 

The Sears guy is right, except for the mileage part. You're not going to gain anything noticeable with just a muffler swap and a cold air intake, especially without a tune.

 

Ok thanks, I guess I'll have a Magnaflow put on just for the sound then..is the 22 inch similar in volume to the 2004-2008 factory muffler? I found an audio clip on here with the same muffler-only install on a similar year as mine, but I can't really tell from it.

 

It will be extremely quiet, possibly too quiet. I would suggest an 18" oval body. The 4 cat system is what will keep the 18" tame enough.

 

More quiet than the factory 2004-2008 muffler? I like the sound level of that one.

 

The 22" might be as quiet as the 2004-2005 trucks but with that Magnaflow tone. The late 2005's-2008's only have 2 cats, so they sound slightly louder.

 

Do a 14"!!!!

 

Getting the truck to breath better is a good start. So a CAI and a free-flowing exhaust will get things going. A good tuner however, will get you better results like 4.6 said. Since you're having issues with the trans shifting into O/D, I assume your either towing something, or have oversized rubber. In that case a tuner with a tow tune as one of your options would definitely help there. That being said, your 4 cats are the biggest problem. I had a quad cat set-up before and replacing them with 2 high flows made a big difference for my truck. Keep in mind that doing so will have an increase in the db department.

 

That would be great for me, I don't want anything too much louder..got that out of my system with Flowmasters on the Mustangs I used to have.

 

I don't do any towing and I have very close to factory diameter tires, I have the downshifting when the hills get steep is all. Are you saying if I take two of the catalytic converters off the exhaust would flow much better, or would that just be for sound?

 

Your quad cat system is highly restrictive, swapping them with two high-flows will yield much better CFM numbers, and will accordingly give you better performance and throttle response......better sound in my opinion also, but will be louder. A larger diameter oval muffler should keep things on the quieter side.

 

Oh sorry, not just 2 of your cats....swap all four for two high-flows.

 

A programmer would be better for performance if that's your main goal. If you can get all of it done (muffler, CAI, cats, programmer), then it will perform much better. Hi-flow cats will make it louder and more aggressive.

 

Ok how does that work, do I buy that as a kit with the pipes included, or just install two converters into the original pipes?

 

I used to have a programmer with one of my Mustangs, manual transmission..didn't notice anything at all with that. I was thinking a programmer would help with shift firmness, but that's probably it..I'm not planning on modding so much that I would really benefit from a custom tune.