Besides the actual look and set up for 4-2-1, or 4-1 headers. Does one header set-up perform better than the other? what is the difference between them besides look, since they are basically the same price for teh same product.

 

With the cat in the stock location, it's traditionally accepted that 4-2-1 allow for more midrange torque while the 4-1 helps with high-end. The very best setup NA, as I understand it, is a 4-2-1 with extremely long primaries (ie just about as long as the standard 4-1), and the cat is pushed back about a foot or so to allow for the 2-1 convergence.

With a supercharger, you want a 4-2-1 with extremely fat and short primaries.