TM headers says that their product makes 20hp and 35-40 ft. lbs on a completely stock vehicle. More potential with other mods. I know it sounds pretty outrageous, but the factory manifolds on the explorer are complete crap. Three cylinders go into one tube down to the collector.

I would say they are correct in those gains, as my Explorer hauls ass now (for an explorer). I have removed my rear cats and installed a dual in dual out magnaflow muffler. I also have a MAC intake and comp cams camshaft installed.

My explorer is a 2 door sport model. You couldn't buy them with a V8 from the factory, and I wanted a V8, so I got a rolled 2000 mercury mountaineer 5.0 AWD and swapped the drivetrain in. My explorer had 4.10 gears from the factory and the mountaineer had 3.73's, so I stayed with the 4.10's and that helped my acceleration also.

My dad has a 99 mountaineer 5.0 and the difference between our trucks is pretty extreme.