Hi - I have a YZF-R125 as well with the full Yamaha accessory kit. having recently passed my bike test I have asked two local Yammy dealers about de-restricting my bike as I now want a bit more oomph having ridden a 500cc machine . Oh boy,pork sandwich at a bamitsiva comes to mind...... Not gone down well. The general opion is that a "Race Exhaust" would at best add about 3hp. To re-map the ECU would be be as expensive. So I would say its probaly not worth spending hard earned money trying to get any more out of your machine.