Just for interest, I have both green and red manuals. They contradict one another in the section on adjusting your CO content (Digifant models). One states to turn the adjusting screw clockwise and the other states turn it anti-clockwise. I was trying to reduce my CO content using the instructions in the green manual and ended up with a CO content of 8.5% (should be 1%). Only realised the mistake when my car was running sh..e and I borrowed my neighbours CO analyser. I bought the red book recently on ebay for about £7.00, it certainly is a lot thinner than the green one.