K&N Cold Air Intake System: High-Flow Air-Filter, Increase Performance & Horsepower: Compatible with 2002-2005 CHEVROLET TrailBlazer; 2002-2005 GMC Envoy; 2002-2004 OLDSMOBILE Bravada, 77-3036KP

Absolutely am thrilled with the performance difference, even here in California with its tougher air quality compliance rules K&N knocked it out of the park!My 04 Trailblazer LS sounds 'mean' and I readily noticed the increase in horsepower. Easy to install, except cutting the hole opening in the round tube to insert the grommet in preparation for the elbow piece. Using the specified 1.25 inch hole saw the opening was too small, so I had to use my dremmel to grind and enlarge the opening, then with a little lithium grease the grommet slide in. Job completed.

Easy install. Great instructions. Very happy and satisfied with performance of my 2005 Trailblazer EXT I6 4.2L.Engine sounds great.I cleaned the throttle body while i had the air filter intake off the engine, so double nice :)

Good product. easy to install. increased hp and towing capacity, but no noticable gain in mpg. It does sound great under the hood though!

Please note the update below. My reasoning for a 1-star review is there.I bought this intake at a great price after researching it on K&N's website and reading the installation sheet thoroughly to make sure it would be something I wanted to to and could do.The big thing that most people will have to do with this particular application is drill a 1.25" hole into the tube. Not exactly what most people think they'll have to do. It wasn't that bad but it was a little unnerving considering if I screwed it up, there goes the whole project. You have to cut the vent tube prior to this, so after that, you ARE committed without having to buy replacement hose(s).Other than the above, installation was easy, if not tedious due to following all 22 steps, in order.Make sure to re-tighten all fittings after your road test, and re-check them again after the first day of driving.UPDATE: June 29, 2013I have taken my 2005 GMC Envoy back to stock. Any acceleration gains started dropping off a few months ago, and my gas mileage went from bad to worse. Before I returned the vehicle back to stock, I was barely getting 11/mpg. Not a typo. Eleven. If you enjoy a loud intake with minimal gain, and horrible gas mileage, then by all means purchase this product.Having satisfied my curiosity and eating a big slice of humble pie, I can fully and with all the conviction in the world say to you, "AVOID AT ALL COSTS".

I would barely consider myself a "weekend warrior", but this went on way too easy! It took me about 90 min from start to finish. No problems at all. The sound of my Trailblazer is roughly the same at idle, but has a bit of a deeper, throaty tone when I get on the pedal. I haven't had it long enough to know if MPGs will change. I do know that it has already made driving my vehicle even more fun.

Really helped the performance but didn't do anything at all for the MPG, maybe a little worse! This was on a 03 trailblazer.

I LOVE this thing so much. It was actually fairly simple to install, with the only hard part being the 1-1/4" hole I had to drill out, but other than that, it took me around 30 minutes I wanna say to install this. I have a 04' GMC Envoy with the 4.2L I6 engine. And it fit perfectly. The thing that put a huge smile on my face was when you gave it gas. The beautiful roar that came from the engine was just amazing. I definitely felt a performance gain and it makes your vehicle a lot louder.. It sounds SO good, I can't even explain it. I'd definitely recommend this for your vehicle, you seriously won't regret it at all!

Goes all the way to the intake manifold not just to the plenum. Trailblazer performs and sounds a lot crisper