Not sure where these 8k figures come from, if you are competant with a welder and spanners you can do it for a fraction of the cost!
Not sure what the kit costs from K-Tec but I guess its not cheap? but I supose it takes a lot of the messing around and fabricating away.
As For fuel mines fairly heavy, cost £96.00 to drive to pod do a few runs and drive back... Thats about 450 - 500 miles all in... And most of that was cruising on the motorway...
If im blasting around on short trips it'll eat a tank in about 150-200 miles.
The thing is I wouldn't do it to my everyday car, its ok if its a weekend car...