Does anyone know what this part is called on a ng engine

[IHK 11]

Hi i have a 1990 Audi coupe 2.3e 5 cylinder 10 valve which has an oil leak and i think its coming from a part which is attached to the side of the engine which may have a gasket i could replace but i dont know what this part is called. I was hoping someone on here might know? Thanks. Its the silver metal piece that is bolted to the side of the engine under the black hose. Thanks.

[daveyboy1967]

Under the thick black hose or the thin one Ian?