Well I tell you what I've done to my RM125 to make it so no other 125's keep up.
I have to drop in rings more often than others but still I get the performance I need.
I have Bill's Pipes works Pipe and Silencer, also Had Bill's Pipes Port and Polish the Cyclinder. ( A huge power difference )
I also changd the stock gearing about a 4 teeth bigger in the rear and a 14 tooth in the front. I threw in V-Force Reeds to give it the full effect. This gave it an explosive bottom and never bogs out. It should always be in the power band.
This is what i'vs done to make my 125 the bike to ride. Good Luck. let me know if this helps.