I wanted to reply to this thread since I also had to replace my coolant pipe assembly (or "water guide housing"), and there doesn't seem to be any mention of this repair anywhere else online. I'm guessing not many people have issues with this part, so we're in the unlucky few.
My '05 Boxster 2.7 developed a coolant leak roughly a week after I completed a preventative water pump replacement. I noticed the leak under the front of the engine and assumed that the new pump was the culprit. Turns out the coolant pipe assembly was seeping from the top, due to a bad seal. I tried drain