Did you get it figured out yet? Don't give up! Did you check the fuel pressure? Maybe a bad fuel pump? The lean plugs kinda point to that,along with the cutting out under load. The best way to figure this out is to get a chiltons manual for the motor and your truck and check out how the previous owner wired it in. How did he merge the truck wiring with the engine wiring to make it all work. Your going to have to go over everything like you did the install.