pdub42 -
Welcome to EM! If you have a 1995 Eclipse, there is no guarantee that the OBD-II protocol is working correctly. The Kiwi and the Scangauge need the OBD-II protocol to work correctly. That didn't become law until 1996, so your Eclipse may be on the cusp. Until 1996, it was up to the manufacturer to implement the protocol at their discretion.
In terms of coasting in neutral at 55 MPH, the Kiwi should give you MPG in the 80s or above. I don't see the behavior you are describing with my scangauge.
Here is a bushel of threads on the Kiwi :
http://ecomodder.com/forum/showthrea...mpg-10235.html
http://ecomodder.com/forum/showthrea...-mpg-8447.html
http://ecomodder.com/forum/showthrea...-mpg-7389.html
I think the Kiwi is at fault, but the year of your car is a stickler.
I looked up your Eclipse. A 2.0 liter 5-speed weighing in at about 2700 lbs. That's close to my car, except I am at 2456 lbs, so I am a little lighter. I think you have a great platform to work with. I am guessing that you will be able to average in the high 30's without any modding.
What is your driving context/commute like? If it's a lotta short trips and/or city, that's a killer.
CarloSW2