I notice that many of the reviews on the Avalanche mention low or poor mileage and little power, well I just had to reply and say "K&N". I've had my 'lanche for two years and the K&N intake system for almost 15 months. On our recent long highway trip this summer from AZ to OK we got 21 to 21.5 MPG, with the AC running, two people, with the truck bed loaded with gear. The mileage was just as good last spring with 4 people and camping gear from Tuscon to Albequ. Power? What an improvement. With the K&N system throttle response is almost immediate. Oh, I have the 1500, Z71 package. ADVICE: If you get the K&N system don't bother the intake tube that comes with the kit. Keep the one that's in the vehicle. My wife didn't like increased engine noise from under the hood and I thought the new intake tube was a little to close to the radiator fan.
The only problem I am having is getting the thermostat control working correctly (for the passenger compartment). When the heat comes on it seems to stay on... 4 more on that feel free to write me. durhamj@cox.net I also have a small rattle in the midgat..

AS an update:
The front seats are plenty for my 6'4", 210lbs frame. We use to have a full size van, the avalanche rides smoother. Changing to 4WD is easy, you just push a button. And price, I always wanted a Tahoe, since '92 that is, but when I saw the price of Tahoes in this area (45K$ plus) we had to reconsider.
On the minus side I have to mention the front passenger seat. It doesn't fully recline like the captains chairs in our van, or the seats in our KIA Sorento.
Amount Paid (US$): 33500
Condition: New
Model Year: 2002
Model and Options: 1500, Z71