Just putting this up here for the archives if anyone searches for this issue. This may be common knowledge to real mechanics but it’s the first time I became aware this part exists.
After 100K miles; my wifes Cavelier developed a very strong smell of feul inside the cabin. Issue turned out to be the O rings on the Feul pressure regulator had failed. This is on the top front of the engine directly above where the oil filter cap is. It’s about the size of a visine bottle. Fuel line comes in one side and it’s connected to a long silverish tube. Mileage had dropped from the 360-380 range to about 245 per tank. Popped hood and ran the car and saw the feul running down around the silver tube.
FUEL SYSTEM IS UNDER PRESSURE! DEPRESSURIZE!
Got a high pressure blast right to the eyes. 
If any real mechanics would like to add helpful info; please feel free.