When working on the fuel supply/injection system, pay careful attention to the following "6 rules":

WARNING: This page is about a different variant/trim than selected.

Thoroughly clean all connections and the surrounding area before disconnecting.
Place parts that have been removed on a clean surface and cover them. Do not use fluffy cloths!
Carefully cover opened components or seal them, if repairs are not performed immediately.
Only install clean components: Only unpack replacement parts immediately prior to installation. Do not use parts that have been stored loose (e.g. in tool boxes etc.).

When the system is open: Avoid working with compressed air if possible. Do not move the vehicle unless absolutely necessary.
Separated electrical connections: Protect from dirt and moisture. Connect only when dry.