I have a 03' vibe with 24,000 miles on it and my mileage started going from 400 per tank to 250 about 10,000 miles ago and that ALL HIGHWAY! 1. Is anyone else having/had this problem and knows what the fix is?I have taken it to 2 yes 2 dealerships and they have NO CLUE!PLEASE HELP - It is costing me...