I played around with mine the other day. Took it apart just to see how it was built.Draw through stem seemed restricted.The tenon on these are a lot like a Grabow Ajustomatic and have the same thread pitch. A Grabow stem will screw right in. Anyway,pulled the stinger out,no inprovement,so I removed the tenon,which screws into the stem,unlike a Grabow. The tenon was not drilled completely through the size of the stinger,it was smaller at the end. Opened that up to 1/8",put the pipe back together and the draw was still tight. Removed the cap on the end of that aluminum section and could see that that hole wasn't drilled all the way through either. Opened it up with a 1/4" bit. Draw is better,but the hole in the screw that holds the bowl on needs to be opened also. It's to small to open up much though. Mine must have been made on a Monday or Friday!