When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Intake temp sensor maybe? ECU uses them. Not sure if S4s differ from S5s, but I know S5s have two, one if the AFM and one in the intake manifold, where the UIM and dynamic chamber meet.