Crap! Another "miracle" device with a whole ton of butt-dyno testamonials and no A-B-A testing. When I get my MID I'm going to test a catch can. I don't care if I have to drive all day to get some kind of result!
The subtracted gunk is probably good for 1-2 mpg on a regular basis, which is what I'm thinking the catch can is mostly going to do. 7 mpg extra in a truck? pfft...I wonder how hot it was that day.
I think we really need to educate people on the variability of FE - especially due to temperature - and that checking "once in a while" isn't good enough. Everyone I talk to about it has no idea how much it jumps around. I didn't even know until I bought the Metro and started researching it.