Have you removed the heat shielding on the exhaust manifold or changed the route of the fuel lines . It sounds like your heating the fuel before it gets to the injectors and causing it to turn to a gaseous state before it can be atomized by the injectors. Look for places on the fuel lines were they come close to the exhaust pipes or the exhaust manifold. The codes your getting are a result of the engine running poorly not whats causing the engine to run bad . the p0420 indicates your plugging your catalytic converter. the p0128 is a temp sensor which is telling you the engines not reaching op temp and the last one is a crank position sensor indicating the spark cannot be fired at the proper time . If you continue to run the truck the way its running now you will probably need to replace the catalytic converter ,as your plugging it with raw unburnt fuel . Hope this helps