Cadillac: cadillac 1995 deville 4.9L --MPG is way down, vacuum lines, fuel mileage

Question
I cleaned dirty throttle body and the light "check engine soon" went off, so cleaning solved the problem. Before cleaning, computer was showing like 17mpg, but now it is around 10  Is it even possible? Could i mess up or is it something else? Any help would be much appreciated.

Answer
Do NOT pay any attention to the computer readout MPG panel as they never worked right from the day they introduced them.

Does the engine run OK ?.

Did you put all the vacuum lines back on correctly ?.

Check your fuel mileage via the speedometer mileage like we did in the old days.


tom