i'll tell you one thing about propane, i did an experemint with it not too long ago with just a camp fuel bottle and a blow torch nozzle. I ran a hose from the nozzle to my intake, through the firewall, and drove around town. No increase in power. or noticeable mileage. The next day i drove to the beach with my buddy to do some surfing, and on the way there with a full tank running the propane we used about an 1/8 of a tank. From my house to the beach is probably 60 or 70 miles. On the way home we ran no propane and used 1/4 of a tank. That seems to me to be a darn good increase in mileage with just a low pressure system. Also i forgot to mention that we were going about 70 on cruise control stopping ever 4 miles on the toll way and going through a small town.