On the past few engines I modded, most recently, 2 Axial .28 Spec1 RRs, I did not alter the timing profiles. I did entirely sleeve work and did flow mods and touch-up work on my RR sleeves. In particular, I matched the exhaust port of the sleeve to the exhaust port of the block. From looking through the back nozzle, an unaltered sleeve is poorly matched to the block port; you can literally see a whole ot of brass sticking out where it should not be at all.