I had the vibration with the K1 also and it was because the exhaust was touching a W-Brace under the car.
A well designed exhaust should not be touching anything apart from downpipes and exhaust bungs.
For example, on my Invidia, on the driver side the pipe goes over the ARB and although it's tight, it won't touch.
If you however feel inclined to go to JapSpeed and claim dodgy fitment, they will tell you your car isn't straight rather than your exhaust...