Coverting my 4.4i x5 to gas/compress natural gas (CNG)

[reg]

With gas prices going up again a local radio station ran an interview with a local business owner that converted his entire gas fleet of trucks to a dual fuel gas and natural gas CNG system. Sounds pretty cool especially drive a 4.4i 5 around in city traffic. I also see more and more gas stations in my area offering natural gas. The price now for CNG is around $2.00 per gallon equivalent in the metro Chicagoland area as opposed to $4.10 for premium unleaded. I found this conversion kit that said it can be added to any gas fuel injected vehicle. I was wondering if anyone has done it to their vehicle. Looks pretty promising, however I worry how the x5 engine management system will react to this system. Another downside is you lose a lot of trunk space for the tank.

Any thoughts?
http://www.youtube.com/watch?feature...&v=moX504qJBZc