1: For your QEV cannon help go
here
2: You can't turn a FE in to air, try as you might.
If you're wondering how you can use a FE as a chamber, well, just go
here.
It's amazing, the search feature, it allows you to LOOK BACK IN TIME at everything ever posted on this forum. But that's not all, it means you can do RESEARCH. I can't even count the number of times someone on the forum has used an FE as a chamber, hell I've even done it twice, so why don't you search that for me and come back and tell me exactly how many times its been done.
I'm starting to get sick of this you know, you keep asking questions which have been answered over and over and over instead of bothering to search properly. We can't spoonfeed you steps to making a QEV cannon either, it's so damn simple one can figure it out themselves. You get a QEV, chamber, barrel and pilot valve. Join it all together. Done.
edit: I'm sure someone will be annoyed I used the typical "UTFSE" response but something like a fire extinguisher would be very easy to search. Type "fire extinguisher" click "search for all terms", limit the search to a particular section (pneumatic showcase, pneumatic discussion, construction materials, general discussion, how-to database) and search through them one at a time.