Here is the second mod that I mentioned earlier. It deals with the Y-pipe to cat back specifically. Here are the OEM and URD
4x4 Y-pipe next to each other.
The point of interest is the flange where the Y-pipes mate to the catback exhaust. As you can see, they both bottle neck down, right before that flange. Now the URD is much improved over the OEM, due to being made out of 304 SS and having all mandrel bends. Equals less flow restiction and better power. However, due to the fact that URD had to design it to fit with all forms of aftermarket catbacks, having that flange with bottle neck was a necessary choice.
Gadget even admits that when he designed it, the intent was for those that wanted to go the extra step and improve upon it just that much more, it would be very easy.
This is what my was done to remove that restriction after my friend and I discussed how he should go about building his exhaust.
Now, this is more for those that decide to run the 3" catback, but the same principles apply for someone who wanted to run a 2.5" catback as well.
Cut the flange off at the restriction. Weld on a 3" V-band flange. Weld on a short piece of 3" exhaust tubing. Straight through and you will feel an improvement in the power band.