i used the smarty jr to restore timing the cam to restore exhaust valve timing and the ddp 50's to restore duration and minimize the 3rd injection pulse. the combination gave 4. 5 mpg increase and my oil is no longer solid black after 10 minutes. all of the mod's were to increase mpg. we tow and i can tell you this, these mods give a huge torque gain. it is a trailer pullers dream. as far as horse power goes i do not think i have ever had it over 2700 rpm under load and the dyno testing was done at 2025 rpm and 100 hp jexum on the first truck i changed the cam and dynode then changed the nozzles and tested again but this was at the 100 hp or towing equivalent load at 65 mph most of our long trips are pulling 5th wheel or gooseneck on some 400 mile round trips empty, no trailer to albuquerque i was at 14 to 15 mpg stock now at about 23 mpg if the dyno results follow the same ratio i would say that the cam ddp and smarty was nearly equal. and probably more than the 4. 5 that i stated. the intake side of turbo mods was very hard to estimate empty and the wind made the towing figures fly all over the place at first then we discovered we could test some items like the tag on the dyno. the cool hose with a thermometer and by blocking the tube on the psm i could compare by thermometer. also the air tabs, 1500 tail gate spoiler, tonneau cover could not be tested on dyno. the truck set up for the 5th wheel has the taylor wing instead of cover and spoiler. 95% of its miles is hooked to the trailer. i tried a ats a 3000 turbo on it with disastrous results. lost about half of my low end torque lost mpg threw p0299 codes smoked and ats no help. i am at 18 lbs boost and 850* egt average towing with the he351 and i think this truck could improve a little in mpg so i am trying one more time. i just installed a htt 62 65 13 ss with ss manifold and both the manifold and exhaust turbo housing wrapped in a insulated blanket. to keep the exhaust from contracting. but i have not been able to test it yet. the he351 on the other truck is perfect for it