Re: what i pulled out of my downstem
That stuff is just a plastic residue that coats the inside of various steel products and is intended to prevent rust while it is awaiting it's final sale and/or serve as a releasing agent during the production process. Some of the bottling equipment I deal with has that sort of stuff in it and we run a special solution under pressure to get rid of it before using the equipment for food processing.
The stuff is actually difficult to get out without a good hose brush and a lot of hot water. If you buy a Chinese rig you best scrub the interior until you get it all out because you don't want to inhale smoldering plastics. Plan on spending quite awhile to get it out.
I've never seen that sort of thing in a rig made outside of China.