1999 Ford Explorer Engine runs rough at speed

The engine is running rough when it is up to speed. It has good pick up and seems to idea ok. I checked both coils with the ohms meter and they are ok. I do smell the odor of gas fumes at start up at the rear of the vehicle.

The other thing I was trying to do was change the PVC valve. I am sure it is the orginal PVC in the car. My book tells me it is located behind the intake manifold, however not only is it very hard to see back there, I can't seem to find it.

Any suggestions on both of these problems

Don