Haders and fuel mileage
 

I was wondering if anyone has installed headers of any sort on the 460 efi and seen noticeable power/mileage gains from it? I read torque gains but what are you seeing in fuel consumption and other mods? Is the exhaust upgraded to 2 1/2 or 3 inch and muffler or cat upgrade or stock with headers? What works well with the exhaust upgrades on the EFIs? What brands give you the best product? Do you have to play with timing or anything to get headers to run cool enough or is heat not an issue?