I don't know if Tony does this as a commercial exercise but I'd go for this ...
http://www.airguntech.com/?p=214
The problem with the well known best tuners is time. The waiting lists are very long. I spoke to Steve at V Mach yesterday and he's very very busy plus he's moving premises so he told me to give him a ring again in a few weeks to see where he's up to.
One of my Venom 77s is playing up so I want that looking at but don't know whether I can wait as I only get to shoot over winter.