Lots of things could be going on. In addition to what jcz is saying.....I would look at......
Adding back pressure with your hands cupped around the end of the call.....crow calls don't just play themselves by blowing on them (Not trying to be blunt, just comparing them to short reed goose calls and the likes)
You may have cut too far into the toneboards to where they are causing problems for the reed? Either cut the reed, or the o-ring is sitting on the reed.
The exhaust ends of the toneboard are not being held tightly together in the barrel.
Your barrel is too short. I like 3 1/2" for a starting point, and longer from there.
Plastic guts are never going to sound as good as a nice set of wood guts.....though that cazoo sound will still help make a turkey gobble.
That's some of my thoughts on it. I hope you end up with what you're looking for when you get done playing with them! I enjoy making them to make turkeys gobble. :)
Vince