Couple of easy things you can do include drilling out the venturi as much as possible. I'll have to look and see if I can find the size it will tolerate again, but the info is out there. Then find a dual port (TeeDee) piston/cylinder set. Try smaller props like a 5/3. A balloon tank is probably the best choice for consistent running. And be sure the piston ball socket is snug. Use a reset tool if it isn't free of slack. Still won't be as good as a Norvel, but much better.

Edit: I thought I could find it. Here's bunch of good stuff about the HV.

http://www.clstunt.com/htdocs/dcforu...ID1/11216.html