Gibson GP129S Stainless Steel Performance Header

The worst part about the upgrade was getting the stock system off. But after reading reviews about bolts breaking off, I invested in a $5 can of penetrating oil and sprayed all of the bolts 1-day before starting the project. The bolts came out without a problem and the old system removed. The Gibson Headers went on easily with no obstruction or alterations needed. I recommend replacing the O2 sensors with the new headers prior to installation as this will be an issue you won't have to deal with it once the new system is installed. Gibson also suppies all new hardware with an additional donut gasket, if needed.The swap-out took about 2 hours from start to finish and the end result is fanstastic. The truck runs and sounds much better and definitely has more power. This is a high quality product that's worth the time and investment for someone wanting more performance without sacrificing fuel economy. HIGHLY recommended!

Installed on 2013 Sierra 1500 with 5.3L. Subtle difference to the good compared to the factory manifolds. A bit more throatier & noticeably more responsive at highway speeds. Although, I don't think that the new headers are that discernably louder than factory.Installation was straight forward & a direct bolt on. No need to reuse factory exhaust donut. Headers have one built-in on the passenger side. Good idea to review the instructions that come with. It gets you pointed in the right direction.Gibson quality is superb by the way. Also saved $100 compared to other aftermarket parts websites. Box arrived as sealed from the factory.

Get rid of the rusty stock manifolds and bolt these on! Stock manifolds were rusty and a pain to remove, if you have broken bolts! I live in the mid-west and salt was not kind to the OE manifolds. I have had these on for a couple months now, mpg didn't improve but horsepower and torque did increase. I do a lot of hauling with a 20' tri-axle trailer and noticed that my transmission shifts smoother after installing these headers... stocks were leaking bad at rear of block so Gibson upgrade is soothing to listen to as it quietly rumbles in the driveway when warming up my truck! 4 stars because I had to go to my local know how to buy the donut gasket as it was not in the box, also the flange seems to "sit" on the edge of the heat shield for the spark plugs. Welds are thorough. Gonna buy again for my other truck!

Spot on for my 2007 Hummer H2, I love the amazon garage feature. I just plugged in the specs of my Hummer and ordered. Perfect fit. I of course had an expert install and all is good. Fantastic headers. Purchased same Headers 2 years ago for our 2004 Ford F-150. Fit perfect. Our mechanic said both were easy install.

Rust everywhere after 1 1/2 weeks of installation. Supposedly stainless steel. Plus it came with dents everywhere. NOT A GOOD PRODUCT.

let me start this off by stating that gibson really needs to be more detail with their instructions. the video they post is a complete waste of time to get you to buy the headers getting you to think it’ll be easy. i’m very mechanical but the driver side of the y-pipe was probably the biggest pain i’ve ever come across. had to have someone underneath pull the exhaust pipe out the way while i thumbed the head bolts on, then had to pry the flange end over a good 1/4 inch to slide the bolts through. slipped a gasket between the flanges and it’s still leaking for some reason. will figure that out in the next day or so.. make sure you have a good swivel for impact along with a few extensions to get around the cats. passenger side has the o2 sensor right in the way of an exhaust bolt that you can only get to with a small wrench if you forgo removing the sensor. the headers them selves feel nice and look good. my exhaust note with the flowmaster super40 has smoothed out and the drone has vanished. shifting response also feels better for some reason which i like.it’s a good show watching the pipes smoke when you hear them up for the first time. :DUPDATE: i decided to take my sierra 1500 in to a custom exhaust shop to fix the leak. they decided to cut the exhaust piping on the drivers side and add a section to relieve the tension. worked like a charm.also they cut me a deal on a magnaflow muffler for the better flow. happy with the end result. pissed about the hassle of the “direct bolt on” bs they pushed.Good luck.

These stainless headers are a great upgrade from the stock manifold I installed them on my 03 avalanche 1500 5.3l they were bat that difficult to install. The only challenge came when both rear manifold bolts on each side were already snapped off in the head when I got there but my neighbor is a welder and was able to weld a Alan head bolt on the broken stud and back them out . But after those came out install wasn't overly difficult

2005 Chevy Avalanche Z71 They’re direct fit but you also need to change out the gaskets and studs, light sound change but definitely gives more hp