IMO a 30% loss through the drivetrain is to be expected when puting your car on a dyno, which your car sits pretty close to.
Another thing to consider is that no two dynos will read the same, some read high and some read low. My R33 has zero power mods, and the few times I have put my car on the dyno I have got anywhere between 145 rwkW and 153 rwkW. Considering that the two dynos are around the corner from each other, I don't think a slight change in location can equate a 8kW gain