You have probably done this already. I noticed with my BT injector I get a lot of plastic debris behind the plunger versus say the CC injector in which I get none. I changed the o-rings on my BT injector and it has helped some. I just think the tolerances are not as tight. I tend to get more air in the baits that I shoot with it too as a consequence. I also noticed that as I draw my cup down and get closer to the bottom I tend to pick up some air. So, I have stopped drawing my cup down past a certain point and this helps too.