[Domman56]

OK This is my area of expertise.

Firstly if you're going to claim it helped provide A-B-A testing before and after. Some things work for some on here that don't work as well for others.

My baby right now is a 2004 CLK55 AMG Cabrio that I drag race twice a month, Take on canyon runs, at least once a month if not more. Also I'm a heavy footed person naturally. However I still average 18.5-19 MPG out of it Even while having fun with it. Mods ( K&N filters, Secondary Cats & Resonator Delete, Flowmaster Super 44 Muffler. Transmission internals from European spec CLK along with Tune to delete top speed limiter.)

Firstly Intake and exhaust DOES NOT garuntee mileage on all cars. As you said you're not exactly light footed on it so that is where these mods MIGHT improve your mileage. Then again there's no garuntee.

A CAI pulls in Colder Denser air therefore telling your computer to add fuel to match the A/F ratio. Now here's why it works for heavy footed drivers. 300 HP is going to have a harder time pulling 5000 LBs than 315 HP will.

If you want to upgrade your muffler I'd NEVER tell anyone not to It may help it may not. Just pick something you like the sound of. I see you're from Texas so my suggestion would be LOUD haha. There are different mufflers that flow better than others of course however sometimes it's worth losing 1 MPG for a better sound or better performance.

When you install your intake (I personally prefer the K&N FIPK) Alot of people also like AEM with a Dryflow filter. Make sure to disconnect your Negative battery cable during install and reconnect it after. This way your computer recognizes the new A/F ratio Immediately.

Either way Intake and Exhaust is a nice way to wake up the V8's in the suburban Have fun with it it's your truck however look into Aero Mods also that's where you will usually get the largest increase