My truck is V6 with a single exhaust. This means that somewhere in the system the exhaust pipes from the two separate engine banks need to be combined. This truck does so with a "Y" pipe. The factory Y pipe is constructed by crimping two circular exhaust tubes into a half circle and jamming them into a third pipe. The result is a very restrictive junction. As we know the more free flowing the exhaust system the better the engine runs. Lets not start an argument about back pressure now. This is an excellent place for a little performance modification. As some of you know I, like many other people, suffer from WYAIT (while you are in there), so while I was getting my crushed exhaust repaired, I might as well address the bad Y junction WIWIT.
Since blending two tubes to make a smooth "Y" junction is not very easy to do, I decided to buy a pre fabricated "Y" pipe. I found that Magnaflow made one that suited my purpose. I took some measurements and decided that the 2" in and 2.5" out was the perfect pipe. I then source the part online for $26.83 from autoanything.com. Perfect.
Shawn's Muffler and Welding in Tahoe City is a local muffler shop. There might better and cheaper muffler shops, and I am sure there are worse and more expensive ones too. However he is close to my work and does pretty good work. He bent and welded in a new section of exhaust pipe as well as the new "Y" section. He charged me one hour for his time and the materials used.
Preliminary result show a return of my MPG and a little more pep. No additional exhaust volume, maybe a deeper tone. Throttle response is a quicker and ass dyno estimates a 5hp gain.