If you haven't already done it, add gauges. Put in some injectors, at least stage 1's. Beans Diesel makes a Dominator 66 turbo, it's the only upgraded turbo for the obs trucks that is a true drop in. If you go bigger than stage 1 injectors you might want to go to a bigger turgo like the H2E, but you'll have to upgrade to the super duty pedastool and intake.