[Biturbos4] new B5 S4

[mike]

Long time no post but my old S4 has been retired at 230k miles and replaced with a "new" one, same age but *only* 100k miles.
new one is doing 22 mpg (old one did 27) so codes were read. 

Seems there are lambda sensors not working plus maf isn't working but strangely, looking at blocks I have 50c inlet air temp which on a cold idling car in the UK is nonsense.
Does anyone know where this temperature reading comes from? Is it MAF?
Cheers
Mike