These headers are great! They look great and sound great too. I installed them professionally, but the silicone pads that came with them have already burned out! They looked cheap and flimsy but I made the mistake of listening to the muffler salesman who assured me they were good. I had to use factory multi-layer steel pads that cannot burn through. When it comes to performance, I can swear it's a definite improvement over the standard! In the past my V-8 2000 Tundra would downshift when towing when coming out of acceleration and chased up and downshifts on inclines at highway speeds (55-60mph). It drove me crazy! Not to mention my gas mileage was terrible! Now that I'm hauling over 4500 pounds, my truck maintains its speed better without constantly shifting up/down unless the incline is long or steep. I can't give fuel economy improvement numbers because the truck is a lot more fun to drive and when I'm not towing I'm holding onto it. At 10-20% throttle at low RPM the thing pulls better than at full throttle; especially in cold weather with 93 octane! I would highly recommend these headers and also encourage you to purchase stainless steel multi-layer exhaust gaskets. An aftermarket like Beck Arnley makes inexpensive gaskets that you can buy on Revain.com in place of Toyota Factory parts. They are cheaper and identical!