Thanks for the welcome other Allan! All the allan's should hang out and do doughies in a carpark sometime, haha.
And yes, it's pretty fun as it is, but another 80 or so bhp would be more fun : ) My daily ride motorbike is a custom gs1200ss with about 133bhp at the wheel and weighing 195kg, so I quite like having a bit of power on hand personally.
I had a chat today with the friend of a friend who had an aftermarket exhaust system approved on his warranty covered car so it is possible, just has to be approved before and negotiated with the warranter.
A tune wouldn't get approved but 'hypothetically speaking' with a cobb accessport and a duplicate of the original map set as one of the map option it could just be switched back should any problems arise... (would speak with jtune and get it set up correctly). I also think with the correct map and some thorough engine inspection and testing prior to doing anything the level of risk isn't that high in terms of the engine going bust from running excessive boost or anything stupid.
What does the bmw powersport pack consist of? I googled it but didn't get a very specific answer (within the three clicks of time I gave it looking).