Expect around 220-320 depending on if there is enough slack in the timing belt for the tuner to slip off the old cam gears and pop on the new ones. Thats fitting and dyno tuning time
rb20 like is more it seems. 5rwkw - 20rwkw can be gained. Silvertop with mild mods went from 190rwkw to 210rwkw at my mechanics workshop last tiem i was there.
But as mentioned previosuly its abotu tunability, and playing with how the power is delivered.
in and ex gears on rb20 typically make 10-15 rwkw. Question though... if getting a workshop to do it, is it worth doing it when replacing timing belt, eg. biiiig labour cost? or is it a matter of loosening and little labor cost involed?