Problem with gaining low rpm power is the percentage of power made from torque at lower rpms, e.g.. 25% at 1,313 rpm, 50% at 2,626 rpm, 75% at 3,939 rpm, 100% at 5,252 rpm etc.. Every rpm has it's own percentage, as rpm goes up percentage gets higher and more importantly for your application vise versa. Which means big torque gains only make small to moderate power gains at low rpms, why diesel are preferred for low rpm power cause of there ability to make huge low rpm torque per Cid.