I have the little hole in the end of the tube in mine too. But I don't have any springs, is the carpet knife supposed to not have any springs? They're different cars so I don't think I can answer your question, but I do believe the hole is supposed to be there. The heaviest shock oil I have right now is 80 weight so I'll just use that untill I can get some 100 or heavier. I don't believe there are any burrs on the insert, but I'll double check, and I did clean out the tube with a Q tip, but I'll do it some more, I'll also try spraying out the damper tube with some motor spray. How would using heavier shock oil in your damper tubes affect the handling on your car? If it does change it at all.