I just acquired an '05 LLY and am disapointed with MPG. This is my first posting so bear with me. I'm sure this has been explored a lot, so I apologize for raising it again but I'm having difficulty trying to figure out what I can do with a limited budget that will give real results. I'm considering some sort of intake system, but am concerned that it won't help much. Also, I'm thinking 4" exhaust but I doubt that cat back would really do anything. I'm not wild about violating MD's emissions requirements by replacing the cat, but may have to. Would installing a larger 4" cat help or does anyone even make one?