If you are unlucky you might have to loosen the exhaust manifold where it bolts on to the cylinder and adjust its position, to get everything to line up right without any stress anywhere. A bit of a bugger to get to those nuts.
No stress is very important for handling the vibrations, otherwise cracks will develop.
And I am certain my scooter is nippier with the Akra, especially with the catalyser removed - but then it gets too noisy. All the German tuning experts fit Akras or Remus exhausts. They test their mods on dynos, and none of them use the strandard exhaust. But on the other hand, they have a lot of mods to the engine, airfilter, etc to go with the easier flow exhaust. I have a modified airfilter and modified injector fuelling on my GTS300.