I have a 1999 Chevy C1500 with a 5.7, and I have replaced the entire ignition system just about, Cap and rotor, plugs, wireset, and coil and Im getting anywhere from 7-10 mpg. I have been blowing through caps and rotors almost monthly, I even tried sealing my last one to make sure moisture wasn't getting in the cap and it only made it worse. And somewhere in 2nd or 3rd gear(dont remember which of the top of my head) it will start missing or something and the tach will show it moving up and down a couple hundred RPMs, you'll even feel the truck slow down and pick back up. Ive tried a block test to check if a head gasket is leaking and it didnt show any signs of combustion gases in my coolant, this problem is literally driving me insane and broke because I cant afford all the gas its needing. Heres a few pictures of the distributor cap, it will do this almost monthly. It wont bring up any codes for it either. Anyone know anything that might help? Thank you.