V85000i
Member
IRS is very easy to do. On the RHS in line with the LHS front muffler exhaust mount, you will need to weld a mount if there isn't already one there. That is the only thing you need to do to the car itself. Off the extractors (if fitted) run twin cats, then two pipes one either side of the tail shaft, into two mufflers or what ever you want there, out the back of those they come together and run side by side under the axle and out the LHS where the original exhaust runs.
These are available off the shelf here. $670 is what I would do it for cats back. They look very similar to the VT-VZ V8 twin system. The front part off the extractors would have to be fabricated unless you hand get hold of a HSV set up that has twin cats.
Sorry to dig up an old thread. But do you still sell these twin systems. Its for a vp calais v8 and how much $$ if ya still sell them