How can the fuel/air mixture be OK if you smell raw gas in the exhaust and you only achieve 13mpg?
The only mechanical part in the engine that could cause anderratic fuel/air mixture is the valve train. Hace you worked on the camshafts? A cam with a few degrees off can cause lots of problems.
Silverstar: They are the one who wanted to replace a heater fan on my car and a climate control mudule on my car. The problem was a blown fuse. Go figure
JackD