Valve under S3 inlet manifold?

Alright mate
not sure what it is called but on my 1999 APY, the bit you describe is called a solenoid changeover valve and the part no is 029906283H and it appears to open and close to control the secondary air inlet combi valve.
 
EGT probe connector box.... fixes to bottom of the inlet mani...

<tuffty/>
 
As tuffty said . The box that is bolted to the bracket under the inlet is the EGT connection box. The aint cheap either,
Ive bought one and didnt like the bill one bit,
 
okay so depends on your engine then whether it is the egt sensor or the solenoid, I see from your previous posts that it has a couple of hoses attached and one has snapped?

Remove the plastic cover, if there is an electrical connection to the left of the dipstick it will the egt sender (G235). If what you are referring to is bolted on the bottom of the metal bracket with an electrical connector and two hoses coming off it then it is probably your solenoid for secondary air inlet.