Im going to be putting stacks on my truck in the near future. Ive already got a set of 5 inch mitre cut stacks from the local trucking company. I am going to be buying the y pipe that comes through the bed off of ebay. I see you can buy a kit that connects to a 4 inch exhaust and one that connects to a 5 inch exhaust. Im just wondering what size exhaust you guys are running on your trucks. does it really matter if i go 4 or 5 inch?. will 1 inch make that much of a difference?.