So I found the issue I believe. After the first code telling me I had an inefficient cat I took it to a local exhaust shop. They did a code reading again. Another code popped up Auto Zone didn't tell me about. Something about an open loop regarding the fuel. He explained that when I first start the truck it's like a choke. It dumps in fuel until the engine comes to temp. then the loop is closed. Well apparently I had not noticed (being I am not the driver) that the temp gauge has been riding at cold for a week or so that's why the gas mileage has been bad. Need to know info.!! Exhaust shop mechanic told me to change the thermostat and see if that will do the job. Did that and now it's running at norm. temp. He said the cats may have been damaged but the only way to know is to drive it and see if it throws up the service engine soon light again. When I took out old thermostat half of it had been cut off from previous owners. They cut away the part with the spring and all. They also put Locktite on the steel bolts that goes into aluminum threads. Tell me I wasn't panicking taking out those bolts.
I wanted to thank you all who answered my call to help. I love forum boards for that exact reason. You're all great in my book.
Cat converter defective
08 FX4... Flowmaster Exhaust, line-X, Sky Jacker leveling kit. 305/55/20 BFG M/T KM2 mounted on 20 X 9 Carol Shelby wheels. AIRAID CAI & Throttle Body Spacer. Projector/Halo headlamps and LED Tails & 3rd brake lights,custom upper and lower Grill. Edge Evolution. Interior/Exterior LED lighting, NFAB step bars.
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