marks. I started by grinding all the casting marks and humps off that I didn't want. Then used an air disc grinder with 120 to get it smooth all over and a dynafile to get in between the runners and take the bit off that stops injector replacement with the plenum on. After that I used 220, 320, and 400 to get it smooth enough to paint so it wouldn't leave any sanding marks. The caliper paint had pretty good body to it so it flowed out nice. Powdercoating is definitely tougher ( and more costly), but the plenum is quite protected so I didn't feel there was any reason it would take much abuse.