As Johnny stated - I did have a system on my old Vectra
Unfortunately it was a very early kit which in the end gave me nothing but grief, it was what got me researching and brought me to this site.
With it being an antiquated bit of kit, noone was willing to fix it - or even look at it for that matter.
It was faulting towards the end of ownership giving me endless limp modes home, I traced it to a bad earth around one of the front struts, putting the fan on - even operating the electric windows caused a power loss and made the car hesitant under steady acceleration. !!!! Enough of my woes
When it was working it was great, limited loss of power (hardly noticeable) and half the price of petrol at the time (unsure now) so depending on how you looked at it, I was saving 50% on costs or running a 60mpg 2.2 to work and back.
Oh and I did have a small leak, sat in a small garage in the morning with a mild gas smell was great, I held my breath everytime I turned the key 🙂
Hope this helps pmsl