A Trek Multitrack is a great utilitarian bike but it's never going to be a lightweight, so don't go throwing away money trying to shave a few grams here and there. There are a few things you can do within reason to improve its speed or ride quality, though. First and foremost, pick tires that suit where and how you ride. If you ride mostly on pavement, for example, you should be riding on tires with fairly smooth tread, like slicks. The lower rolling resistance is easily noticeable.