[CAN Lambda Error 54 Excess pump current]

I recently replaced a sensor due to the same error code and and my AFR going lean and running away. Probably had a few more KMS on it than yours. Fitted a new “motor sport” LSU 4.9 and problem gone. 

[boost switch]

6 hours ago, Adamw said:

You will need another expansion loom.  Or if you no longer use the auto/manual intercooler spray switch you could use one of those DI's for your boost switch.

This^^^^. 
 

This is how I run 2 boost settings. Have the spray icon illuminated on the dash when high boost is activated as well 

[Evo 8 Evolink New Cams Idle]

 

In the attached log your IAT reads -40c and the IAT fuel correction is adding 6 % fuel at idle. 

[Evo 8 air fuel ratio changing by itself]

Would start with looking at your IAT sensor wiring etc. Logs show a value that starts at 3 degrees and goes as low as 1 deg. Surely that's not correct

Also if you haven't gone to far with the initial tune i would suggest starting over with fuel equation mode set to "Modelled".

[Evo 8 air fuel ratio changing by itself]

Tune file??