All you guys posting numbers should post your baseline numbers as well and whether these are corrected to some standard for comparison. I actually wrote an article about SAE correction this after taking my car to a dyno dynamics dyno, which
you can read here.
Beyond whether they are comparable from pull to pull on the same dyno, we all understand that dynos read differently depending on how they load the car measure the torque at the wheels. A car that climbs from 260-300 (+40 hp, a gain of 15%) on a less optimistic dyno will have made more gains than one that went from 280-320 (+40 hp, a gain of a gain of 14%) on a more optimistic dyno. Likely if you lined the two up on the same dyno, the power would be nearly identical (within that 1% of each other). Dyno results only make sense when put into context. We can high five each other all day about some pull, but without context, that pull won't mean as much.