You guessed it, the Gotts mod.
Thanks to all the information on this site, this was an extremely easy upgrade. I spent a grand total of $11.46. It only took me about 20 minutes to do this.
One thing that I did find was that instead of sanding the end of the 3" ABS to fit in the smaller oval opening, I just clamped the pipe to a jig on my tablesaw and ran it through at a very slight angle on two sides, removing just enough to make it fit snugly with just a few taps of a rubber mallet.

 

I can't believe how much smaller the end of the stock piece is.

Sorry for the crappy cell phone pics

 

That is surprising when you take the stock intake out. I had read about how much the mod would increase the size of the intake but a picture is worth a thousand words. I did keep and label the stock piece in case I sell the truck or want to return to stock for some reason.

 

What's the benefit of this?

 

The larger tubing allows the engine to inhale better. The best way to compliment this would be to open up the exhaust a little more