What your experiencing is “NVH” , the headers might be hitting the subframe or a part of the car which then will vibrate into the cabin . Check to see if any of the pipes are resting or touching any part of the car underneath and either adjust the section off the manifold itself or if it’s a design flaw just simply pry between contacted area till there is no contact .

Happy to hear this isn’t just my problem but sorry that it is affecting more people. It took me several days of adjusting and even cutting a half inch off one side of the x pipe before I got mine sorted from a vibration stand point. And I still have a small rattle and the tips stick out too much.

I would take take it back to the shop that installed it. If possible.

I don’t think it’s the cross bar, I think it’s the header touching the heat shield... I can hear the engine idle and belts and pulleys inside the cabin clear as day like it’s pumping the sound through the speakers. I’m going back to the shop late today to sort it out.

So we fixed all the issues.

Throttle pedal vibration was coming from driver side bracket touching the O2 sensor.

Vibrations/sounds were fixed from putting the spacers on the cross bar, and playing with the foil heat shield. It was rubbing pretty bad.

Thanks for for all the help.