I don't have plans or this right now because I just replaced one exhaust manifold but....how much better are headers vrs truck manifolds both through dual exhaust? The engine is a stock 400, 600 cfm 4 barrel Holly, auto, an my only concerns are torgue, mileage, noise, then HP. Rarely get into the 4000 and above revs, 70 % city, 28 % highway, 2 % offroad. So are the truck (fat Rams horn sorta) manifolds that bad?