Niether will gain any MPG. Polishing will not even give you 1millionth of a gallon in a diesel engine. Porting only make things large. Inturn like an gas engine your powerband will be moved up. Smaller ports and cam move the powerband down. Also advancing and retarding cam timing will move your powerband, but I recommend installing it straight up. Factory Cam will run between 600 and 700 bux:censord: . you can go cheaply but a total rebuild of your 7.3 will run about 6k including labor. and most machine shops still won't touch it because it's diesel
Checkout rhino engines 2 year unlimited milage warranty and all 5500.00 after core return 6500.00 and you keep your core. Thats complete drop in from turbo to pan
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