Okay so got it fixed last week, my mechanic took a look at the rerouting option and decided that although he could do it the job was way too complex (read expensive) so he came up with a much simpler solution: heating and then slightly flattening the bottom of the exhaust pipe, then using spacers to drop the plate down just a few millimeters. Boom, vibration gone!

I do have a bit of a concern here though, which is why would the vibration start 2 1/2 years after swapping to the manual and installing (on my new VX) the Kilby plates? I'm a little worried that the motor mounts might be going out and letting the engine lean backwards a bit; is that possible or even likely?