i replaced the egr valve on my 2006 chrysler 300 limited 3.5.the first time i changed it i had a vacuum leak at the dust seal where it went into the upper intake.i took it all apart again and put new gaskets and a dust seal and o ring.now i don't have any leaks or lights on,but now my gas mileage is down from 19.2 when i had the leak to 15.8 with no leak.i'm stumped!!any suggestions?thanks alot for your time.jason