Running into a Hi RPM exhaust noise in my 24 hours of lemons race car. It’s 2.0 DOHC swapped with a TTI shorty header. From about 4,500 RPMs on it gets really loud. I want to do practice track days at a track with a 98 Db limit so I need to get this figured. The header has a donut set up going to a flex pipe. Could engine rotation be causing the donut to loose seal? What are my options?