The valve guide bosses on the inlet and exhaust can be trimmed significantly, the 25mm manifold replaced with a 26 to match the oko.
As grnman said run the ignition on stage 3.
A 32mm big bore pipe will also help.
However... doing all this does unleash a bit more power but it also becomes very twitchy and responsive and needs to be ridden above 7500 rpm the whole time, as when it drops off the ignition advance and cam it has a tendancy to do compression lockups on dirt, motard is different though.