Have you tried adding Lucas fuel system cleaner in your tank? Also check tires, some tires have low rolling resistanace and will not hurt your mpg.
I have tried what others are mentioning and has good results.
I added a camgear a couple of years and advanced it by 2 marks and have noticed that my mpg around the city was better than stock because I don't have to step on the gas pedal as much to get to my desire speed.

Good luck