Hi,

1) X-Pipe is the term we use as well. Why do they cross? Good question, next one please I think it has something to do with the exhaust gas flow...

2) That's the lambda (=oxygen) sensor.

3) See 2.

4) That's the CAT temperature sensor. It controls the symbol in the cockpit instrument (for overheasting). On the ABH it is also linked to the Lambda correction, but not on the PT afair.

Bastian

Das Buch zum Audi V8