The way I see it is a gutted car on the Fto is pointless as the exhaust does not restrict the engine at all. If for some reason you did get pulled over you run a risk of a massive fine. Don't think cops don't notice this as your exhaust just smells like unburnt petrol. You also will be breathing in the toxic fumes when driving and trust me from experience you get it in your throat and it starts to burn sometimes.
It doesnt smell, cops wont notice, if its just punched out it looks stock. However there is one sh*t thing about a decat, you can hear it, the sound reverberates in it and its very audible and sounds pretty sh*t.
This is one thing i love about NZ, it's not illegal to De-Cat your car
My mate got his GPX done a couple of weeks ago, makes a nice sounds change, but not a really noticeable performance gain.
Man '96 FTO GPX
Man '89 Legacy RS Rally car
Man '90 MR2 GT
Auto '08 Fairmont Ghia