My 05 silverado has been misfiring since I bought it. (didn't even notice it when I test drove it) It started off with an intermittent shutter off and on while accelerating, but only at speeds of 45-60mph (miss range) and is now shuttering the whole time from 45-60mph. Once I hit 60mph it stops. No DTC's at all. Hooked it up to the scan tool and shown that it was missing randomly in multiple/every cylinder. I figured it had to be fuel so i ran Lucas Injector cleaner and high test through it, no change. I took the fuel rails and injectors off and soaked/ cleaned them out with fresh gasoline and the problem seemed to go away, but came back that same day. When it misses the WHOLE car shutters help?