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Nope it's original to the car, nothings ever been swapped, all numbers match including a Holden certificate of authenticity, it's a perk of vehicles that shouldn't have been complied on the road is finding out their history
I'm yet to find another VX with an electronic automatic "electrochromatic" rear view mirror (i think they call them electrochromatic or something i think), factory fitted upgraded drive shafts, upgraded V8 Holden exhaust system they were toying around with, my usual dealership i get parts from (and yes they're good for once) can't even find the system on file, car hasn't even got it's own catalogue (you have to enter it manually), plus it's heavier than a standard VX haha, it's just small things.
Well if you have a GMH certificate why are you questioning it on here?
I have a VX II L67 Calais, it came with the V8 diff and heavy duty drive shafts, nothing special there. Been heavy is nothing special, it just costs fuel mileage. I also have a V8 exhaust system, the front half of the original exhaust matches the V8 system (at the cat converters) so this swap was rather easy so again it's not like a lot of thought was put into it, I believe it was so from the VT onwards. The factory L67 exhaust (twin into single after the diff) is somewhat marginal so with the V8 exhaust fitted it would go better than stock as the engine will rev out better.
The problem with the L67 is that when it first came out in the VS it was capable of producing more power/torque than the flagship SS with 304 motor so it is my honest opinion that Holden detuned em and fairly much from then onwards it was so. If you check out the US L67's they make more power stock than ours did for the equivalent model years.