By non-stock I guess I usually refer to when the flow characteristics of the engine have been changed (things like cams, porting, exhaust etc).
You could take this stuff off...but it will have the same effect as stated before. Getting kWs is all well and good, but making the car illegal on the roads and completely screwing the emissions up is not.
It's really just a personal preference. You can go for it, but it's unlikely that you will atually be able to notice the extra power, on a car as heavy as the ST162, you really need to add at least an extra 8-10kW before it makes any noticeable difference.