Exhaust Restriction

[ross79]

I've done a search but can't get a conclusive answer. I will be getting a hayabusa within a few weeks. It's a 2003 with stock exhaust system and stock pipes.
Does anyone know where the greatest restriction lies? Ie is it the stock pipes, the mid-pipes or the headers? Eventually I'll be looking at getting a 4 to 1 on it, but money will be tight for the next few months.