Do you have any special mods to incorporate your chair or can you drive without it? Do you just store your chair or is it actually used to get in/out of vehicle. The reason I ask is sometimes all the mods to incorporate chair features and lift mechanisms are quite heavy and this could be why your MPG isn't all that great. Also, running constantly with the air on full blast will certainly affect MPG! I bet out West it's quite warm right now which means you are probably running the air a lot?
Now our van is pretty quiet actually. When the air is on full blast yes, it's not exactly quiet but it's just like any other car I've owned. With the air on medium or even low it's fine to me, nothing loud about it at all. The ride is nice and even though we've had it a little over one week (too early to tell really) we love it!
This is our "family" vehicle. I also own a Honda Civic which I drive all day long. The van is really my wife's vehicle and our ride to haul the kids around in the evenings if need be. So, it's not going to be driven like crazy which is good because of the poor gas economy. I knew this going in but I was willing to accept that fact for other things more important to us. I still found this van to be the best choice on the market regarding overall value. Second was possibly the Dodge (Drips Oil Doesn't Go Even!) Caravan or Chrysler Town and Country which was still kinda high in price. We had a Plymouth Voyager which was not a good vehicle. I hated it. LEAK CITY! My poor driveway looked like crap all the time. So I didn't want another repeat with the Dodge!
I'm sorry to hear about you poor luck with your Kia. Like I said, time will tell for us but so far it's awesome. People love it and the value cannot be touched IMO. We purchased ours with $4,500 off in rebates! It was only $14,995 and I used the rebates to pay off my Civic! So, still only one car payment! Yippie! So in reality, we paid about $20,000 for the van, which it's worth it to me and it paid off another car. So now We have a 2005 Kia and a 2002 Honda with only one payment of around $360. Not bad I guess.
Well, hopefully your luck will change my friend. If not, sell it and just put an add in the paper to "take over payments". You can always get out from under anything. Heck, even dealerships will pay it off "no matter what you owe" type of thing. I hear them all the time. Wait until December 31st and the car dealerships will do anything you ask!
Chow!