I run from sea level to about 10000 feet when I drive up to Anchorage and other places, gotta cross 3 mountain ranges. I tow moderately, usually twice a week ranging from a 25'x10' tool trailer to a 30', equipment trailer with little excavators and skid steers and such. I'll do some looking into the afc and all that. One of my buddies that has a 12 valve with the 215 pump said he has the 191 DV's and 370 injectors and a #10 plate and says it runs great and only smokes when he dogs it. I've got a month or so before I start in on it, so I'll do some more research. I am going to go with a 62mm S300 though. With an intake and 4inch straight pipe.