Recently bought a cbr600-87

it did ran bad on higher speeds when riding it home. Checked the sparkpluggs and the where wery dry, and a little white. It has a aftermarket pipe and is streetfighter, so it does probably gets way to much air and to little gas due to ,what I guess, is wrong jetting.

so what do you recomend for jetting? anyone with the same mods that knows what jetting they use?
thanks in advance