The aftermarket chip isn't causing any problem, actually it makes it better since the engine will be running at a higher temp. so the sulfur will be burned faster.
The new BMW chip makes it more cleaner and therefore if your cat. converter+O2 sensor are older and not as good as new then it'll cause problems. So don't be afraid, I think the conforti chip will be perfect !!! The best thing you can do for your car (performance) for the money !