Hi, me and my father have a 2003 GTI 1.8T 5 Speed and we are looking to get better gas mileage out of it. I know dual Exhausts would be a good way to improve efficiency but what other modifications would help up the mileage?
chip/tune is the way to go. A boost gauge will let you know when you're in vacuum or boost, staying out of boost will help mileage
However, you must consider the costs of these modifications and the long term pay back time for slightly improved mpg.... if you're worried about saving money then you might think twice, if it's just range, that's a little different.