A word of caution - Do not consider removing the cat unless you understand the implications, you will destroy the engine. You will not improve performance anyway - check out the RC390 forum and all the dyno testing that has been done. If you want to remove the cat you need to install a Power Commander or equal to re-program the ECU fuelling (the experts will tell you this needs to be done with dyno testing for correct results, or you will destroy your valves). The stock bike has been tuned to the optimum (for max power while meeting euro emission standards} and cannot be improved without exceeding those emissions significantly. Not an issue of course if your country has no such restrictions. I am in NZ, where they don't apply, but the cost of trying to achieve minimal power gain is beyond ridiculous.