Yep I knew it, I had a Mac, and it was crap. I had the same issue with my 70mm. I called them; they sent me a 75mm free. And I mailed them back the 70mm. and the darn 75mm had the same issue. Don’t know what it is about it. I got rid of it and a few days later bought me a BBK 70mm. bolted it right on and have never had a single problem with the BBK. If you go to Mac’s website there is a thread some where about this issue and Mac stepped in each time and told the customers to please call them. I’m sure they did the same thing for them as me. Just sent them a new one. Mac is great for the exhaust. There t/b's suck IMO. If I were you I would trash it and get something else, like a BKK. Good luck