As far as a turbo, you'd have to do your own custom fabrication if you really wanted one. Willie's has been very succesful, but your results could vary.
Wheels? Weight is the enemy. Cakley is (still) waiting for some ultra light weight Volk racing wheels from Japan. I would not personally put anything else on the car. Even a tire change is going to cost you at the bare minimum 15mpg. If you went all out and put the largest wheel you could fit with a grippie low profile tire I wouldn't think a 50% decrease in mileage would be out of the question. Also, it would hurt performance a lot. Going to normal tires will totally kill the driveability of the car.
Filters, they make a K&N filter, though I wouldn't recommend one personally due to the fact that they let fine dust particles through. Remember everything is designed towards efficiency, the air box is included in this equation. You could make some sort of cool air intake of your own fairly easily, but you'd probably totally kill off lean burn.
Ground effects, your talking about like a body kit right? No one makes anything for the Insight. Besides why would you want to mess up the .25 CD?
Pretty much anything your going to do has to be custom.
___Have you looked at the Jim Holmgren created Insight footrest and a Husco armrest? The Insight inlayed dead pedal with the appropriate red and black underlayment looks to cool for words and the Husco armrest was practically a necessity for my own commute.
___These two items may not meet your own ideas as far as Insight mods are concerned but the dead pedal in particular should be a part of any properly accessorized Insight imho.
___Wayne R. Gerdes
___Hunt Club Farms Landscaping Ltd.
I have a K&N panel finter on my Insight and can say that it does not allow fine dirt particles through. The filtered side of my airbox is squeeky clean while the pre-filter side is very dusty/dirty. If you want an upgrade that won't hurt mileage, then put a nice audio system in it.
Had some trouble getting through with the link try http://insightaccessories.com/
The shoebox sub and rosta cruise control are two other items of note. Currently we have a member trying to get 5 people together for a supercharger mod. Solar powered cabin ventilation has also been done. Some have gone with the lightweight Honda VX rims. Auto dimming mirrors with temperature and direction readout are also available. Chrome plated stubby antena and MP3 players are other mods. Replacement of the rear wiper with a plug is another. Sylvania blue halogens are another item. Leather seats and steering wheel has been done. Try Catskin. Sorry I don't have links to all this stuff and there is more, but it is all here on this site if you browse around. Have fun.
I was just looking at my Insight yesterday...came up on it from the front about 15 feet away and 1 foot lower...couldn't help but think "dang, that thing looks like it is setting up in the air like a 4x4."
I couldn't help but wonder what effect a front air dam would make. I know it would help the looks but would it help the aerodynamics as well? I know lot's of race cars run very low (scraping the ground) chin spoilers up front to force the air around the car. Probably couldn't do that on the street, but if you had a spoiler that came down 2-3 inches and could lower the car 1" or so??
I am in on the group buy of the Electric Supercharger. I am very excited about it. We are still looking for another person. Anyone interested? Feel free to contact me, coolcat, or Knight for any questions. He already has his test Insight and the ESC is already in development, Anyone ready?