I keep a log of everything that I do to the car, and I have noticed that the intown gas mileage has dropped from a constant 14 mph to 8 mph for the last two tanks. I have also noticed that the exhaust seems to smell rich after i turn it off. I did a quick check under the hood tonight a see nothing wrong. PVC is connected , choke appears to be functioning. This is a 300/327 with a year old edelbrock 600 cfm carb. The power level seems fine. No hard start or run on issues. No back fires. Nothing has been modified to the car other than a oil change in 6 months. What could case this condition. Where should I start checking?