http://liveu-14.vo.llnwd.net/vidilife/image/2005/11/11/53511/1044614L.JPG
Sorry for my bad paint drawing :D

I think a regulator works like that. There is just a stout spring pushing up on a plate that is partially blocking the outlet hole.

With that being said it doesnt seem like it would be ...

Sorry I havn't replied back...

The thumbtacks need to be close together so the spark can jump the gap and ignite the gas inside the chamber. I can't really tell from your pic if they are close enough or not. Try to get a pic of the inside of the bottle.

One wire from the sparker to each thumbtack ...

It's hard to tell from the pic but it looks like your thubtacks are waaay too far apart. Try putting them together more.

So if you look at a cross-section of your bottle the thumbtacks look like this

\ /

You need the gap inbetween them to be just a few mm

If the air tank you are talking about is a paintball tank then the only thing that has 3000 psi in it is the actual tank and that is not the output pressure. There is a regulator on the end of it that drops the pressure down to somewhere inbetween 600-800 psi on a high pressure tank and somewhere ...