I don't know a lot about the products, but the site sure is funny. A quote from one of the pages:
This upgrade part is for the Shocker. I have no idea what this thing does but I am sure it cant hurt your shoebox sized gun. Plus it has an adjustment screw on the front and those are always good.
Honestly, though, I have heard from reliable sources that the Impulse Respirator is a damn good upgrade, especially if you don't already have a tapeworm etc. fitted. And it looks cool, too
And the smokestack, the only evil product I have hands-on experience of, is, well it's just a vert feed extender, but it reeks of quality and the o-ring design is good for anyone who has wobbly revvy syndrome.
Oh, and I want to get my hands on an Omen to play with