Ok So my truck recently was in the shop and had six bad injectors. I sent them to F1 and got Flux ones. When I got my injectors back I had my mechanic do a vavle adjustment. When I got my truck back that was a distinct knocking sound, almost like the old big blocks with headers when they developed a leak but a little more metallic sounding. They say that there is not exhaust leak, but I am not sure. What else could this be? It makes this noise stock, with the pda and with the smarty. I think I heard this noise before, but I dont really remember and since they brought it up I am constantly thinking about it. Do you guys have any ideas as to what it could be? I dont wanna screw up my engine and be out anymore money than I already was for the injector job. Oh yeah I dont really hear this knocking when I rev the engine in park but i can in neutral and drive and reverse. seems to increase in speed as the RPMs go up. Thanks in advance guys, I hope i was thorough enough if not ask me more and I will try to elaborate.