When I took the lower unit off, the Exhaust Loading Tube Assembly (Part #376330) fell out of the upper unit onto the garage floor. I had no idea where it came from until I got a parts list which shows it being part of the Power Head (I think) and it shows it being screwed in from the top. What do I do to put it back on? Do I access it through the Lower Unit or take the Power Head apart? Also what does it do? Thanks in advance for any help you can give me.