No yaccum at tank

When I take my gas cap off there is no sucking sound. There should be some pressure there I believe. 94 4.6 L At higher speeds it seems like the flow of fuel gets interupted when I let off the gas and it has to catch up. Check engine light comes on and then off once it has recovered. Could be a pin hole anywhere in the system causing the lack of vaccum I imagine.

Anyone know of any common leak areas in fuel tank or components that might cause it?

Recent repairs took avg mpg from 16.9 to 19.3 is that about right for that year? Runs to0 good to get much better than that I would think. Still about 9mpg better than that Triton motor in an F 150 so i'll take it gladly.


Any tips are appreciated Thanks