Out of interest, what did the tech do?
All power tubes were original 89 Chinese ones, they were in a horrible state. All of them changed, also completely rebiased the amp according to the best possible SimulClass operation.
Preamp tubes were all also original except one, and all of them were quite of poor quality, all have been swapped for good quality ones, specially V2, which nos has a very fine picked German NOS RFT
Some capacitors were in pretty bad condition too, as the same as some noisy pots and parts here and there, all changed for premium parts.
There was a mod done in the fan (added resistors that made the fan work at half speed I guess), now all that is thrown out and ventilation is far better (mandatory after this revision because now the bias is a lot hotter it seems).
Some little mods and changes are done on the preamp, just for it to be closer to the IIC+ specs, but still with the III rage, this is what I would call the "special sauce" of this revision (this technician is operating Mesa products in Spain since the early 90's, he knows what he is doing).
Sincerely, the amp now is so open, so loose and yet so brutal, I swear it sounds totally like the one on the Ola Englund video.
I'm sorry maybe I'm not being too specific, I'm writing all this using the phone, will try to give more details during this week.