I have a question about the pipe size to HP chart you posted. Being as our trucks (the 05/06 4.0L anyway) make 265HP, that would be 122.5HP per pipe using your guideline (if it were true dual exhaust all the way). So, if I'm reading this right, and I wanted a 2 into 1 system with a single muffler and single tail pipe, I would need the head pipes to be 2.25" running to a "Y" with a 3" output, a 3" in and out muffler and a 3" tail pipe? That's almost what I had with the Banks system with the exception of the Banks has 3" head pipes and a 3" in and out "Y"! This doesn't seem right.
What would the optimal system be for our trucks? I was thinking 2.5" the whole way, but now I'm wondering it it sould be 2.25" to the "Y" and then 2.5" out, through the muffler and the tail pipe! What amI I missing/