I drilled out all holes on both sides with an 18" drill bit. The last one on the right side was the hardest for some reason. I went through two drill bits about $30.00 total. The sound is a little raspy as others have stated but sounds good at idle. No popping or backfire. I cant hear any difference when riding though. I couldn't wait for torque loops and pipes. Looks like it will not be long now and we will have three options- Torq Master, Two Bros and Delkevic.