The only thing I left in the mic was the transformer, the VF14 tube and the K47 capsule, which I actually reversed, preferring the backside. Everything else, I literally gutted and replaced. Every single capacitor and resistor was changed, and I even modified the PSU, as it was supplying too much voltage to the mic.
My biggest problems, which are well documented in Klaus' forum and somewhere on GS, is that the drop resistor T-USA used was overheating the inside of the mic to unacceptable levels. It is my understanding that as a result of my posts on the matter, they will be fixing this in future revisions. I could be wrong though. I wound up using two Caddock film resistors, heatsinked to the body, to rectify that problem.
I found the capacitor selections really poor as well, in terms of material and value choices, and I feel that changing those went a long way to improving the sound of the mic. There was a standing wave in the midrange which I suspected was a result of the BMI electrolytic coupling cap they use in both their 47 and 251 mics. A really horrible sounding cap, that has no business in that position, IMO.
If I learned anything from Klaus, it's that some components definitely sound better than others. Read my interview with him, and that's a point he makes over and over.
I replaced all the metal film resistors with carbon comps, which seem to have a more classic sonic signature, and I replaced the Ohmite Flatso resistors in the capsule bias and grid shunt position with old school spiral carbon, like the originals Neumann used. The metal film might measure quieter than the carbon comps, but I was trying to get more of a vintage sound out of this mic. It surely seemed less strident with the carbon comps.
Oh, and one final thing: I flattened that ridiculous looking dome shape on the basket that the T-USA, Wunder and Wagner mics have. That just looks horrible, and inauthentic. It was driving me nuts.