Hi Addz, I had a cat back exhaust from MIJ for my GS300. At the moment the jury is out as to whether i like it or not. I had the stock set up as i am past being a boy racer but i was looking for a bit of noise when i put my foot down. When i start it up in the garage it sounds great and then i can hardly hear anything other than a sort of rumble which to be honest is giving me a bit of a headache. Then when i put my foot down it sounds more like a wasp in a jamjar. Certainly doesn't sound like a 3 Litre V6 in my opinion. Perhaps i was expecting too much and i may get used to it. If i don't i'm sure the scrap man will love my exhaust!
I have only ever heard good things about MIJ and i thought £495 was a decent price. It's a long drive from Surrey to Walsall though if you want it done there. As they say on the investor forums, DYOR (do your own research). Good luck