I installed a PCV enhancer on 2 of my cars a few months ago, a 1988 Ford Escort and a 1997 Ford Escort. On the '88 I have consistently saw 5-20% increase in mileage over the past 3000-3500 miles and on the '97 it has been driven 1500-2000 highway miles and the average mileage on it has been about 45mpg. The best tank I had ever gotten prior to installing it on the '97 was about 42 or 43 and that was only on one tank. If you will look at where I introduced myself when I joined the Gas Savers you will find I gave specific instructions on how to make one yourself out of a jar that would be thrown away anyway. Will cost less than $10 including the hose to hook it up.
I have just installed an O2 sensor extender and fuel heater in the last 200 miles on the '88 I will be testing the results on them over about a 1500 mile average and will post results at that time.
Neither of these are currently being used with HHO, but that is another project I am currently working on and hopefully be ready to make the installation in a month or two.
I can't promise good results from the PCV enhancer, but I do know it has helped those two cars. I also just added a PCV enhancer to a 2002 Escort my 17 year old son drives, but it hasn't been drove enough to find out what the results are on it. Whenever I get the time I am going to also try it on my wife's 1987 Chevy Celebrity. The reason I initially put one on the '88 is that is was blowing oil into the breather and dirtying up my air filters too quickly and after seeing the results on it I decided to try it on the '97.
The '88 Escort and the '97 Escort are both listed in the garage section if you would like to review the results. Good luck.
It's usually described as a "PCV catch can". Look at Ford Man's profile and his first thread (if you click on his name you can have it show you his threads), or google for it... http://www.google.com/search?q=pcv+catch+can
oh alright I am familiar with catch cans. I have seen some use an air compressor filter with a clear bowl as a catch can. Gotcha. I can't use one because the 2.2L ecotec motors don't have a pcv valve, its vented internally.