I am planing to upgrade 5hp19 gearbox to 6hp19 in audi C5 2.7 TT.
As I seen on forum M7.1.1 2.7TT can be paired with 6hp TCU.
And looking to shematic TCU only need power and canbus to work. Also I see that C6 have samo immo in TCU so I am planing to get everything from late B6 or B7.
Diff gear ratio as far I can see are same on 3.2 FSI C6 and C5 2.7 TT. So I can leave rear diff from C5 on car.

Is this is possible swap to get everything work?

gear rations 3.2 a4b7 box match to 2.0 tfsi a4b7 box witch is understanding turbo load. 2tfsi box is better. or try crossflash 3.2 to 2.0tfsi. I use gearbox, flywheel and torque converter from 3.0 mpi a6c6 but not yet driven with boost. a6c6 2.7t swap.

There is no 3.0mpi in c6

need to try. there is no answer now. the 2.7 turbo ecu works with 6hp19 from NA 3.0, the car drives, but there are problems with not understanding the load of the gearbox. see Stoti thread http://nefariousmotorsports.com/forum/index.php?topic=17945.0