i have a 2014 1500 with the 5.7 and recently had started getting the lifter tick and exhaust leak from the manifolds bolts breaking. I took the cylinder heads off and took them to the machine shop to get the broken manifold bolts removed while they were at the shop i checked the lifters and found 3 that the rollerheads were really loose on so i replaced them and reassembled everything with new gaskets but now when i start it up it runs fine for maybe 30-45 seconds until it reaches idle rpms and then the cel starts flashing and gives me code P0300 and when i put it in gear the whole truck shudders real bad. ive replaced all the spark plugs and the crankshaft sensor but still doing the same thing. i dont think it could be my cam because none of the "damaged" lifters showed any kind of scoring, but any advice would be greatly appreciated

 

Wonder if you have some injector, or coil connectors mixed up...... Flashing CEL is telling you that the engine is misfiring..... Might be interesting to check the misfire counters, and see which cylinders are having an issue.