OK, I'm confused - what should I do? I've got a 2001 1500 QC 4x4 with the 5.9 liter. I want to put Flowmaster dual exhaust on it. Single in dual out side exit. I also am going to gut the cat and install an O2 Simulator. Might put a cutout before the muffler too. From reading on here, most people seem to go with 2.25 or 2.5 in and 2.5 out. The custom exhaust place I called said they almost always do 3" in 2.5 out. Is that going to be a good setup? They said it's 3" coming off the manifold. I'm really not sure which way to go. I want to gain as much performance as I possibly can. Any advice would be greatly appreciated!!!

 

Go with what the shop said. If there is 3" out of the cat, stick with it. There is one pipe in the front exhausting all the gas. After the muffler there are two. The larger lead pipe will keep restriction down. The size is smaller 99 and back.

Brand: Flowmaster
Product Line: Flowmaster Force II Cat-Back Exhaust Systems
Exit Quantity: Single
Exit Location: Side
System Material: Steel
System Finish: Aluminized
System Style: Cat-back
Muffler Included: Yes
Intermediate Pipe Diameter (in): 3.000 in.
Tailpipe Diameter (in): 3.000 in.
Tip Diameter (in): 3.000 in.
Quantity: Sold as a kit.

Exhaust System, Force II, Cat-Back, Aluminized Steel,

 

What kind of performance? Whole shot or Longer? My truck takes 265-75-16 and I put 245-75-16 and you would not believe how fast off the line it is. 30 mph and step on it. HANG ON!!