The car drives better! Hell yes!!
But if you want an accurate figure of power, I'd take it back to the dyno.
Correction SAE J607 is an older standard which did not attempt to include any of the engine's internal friction losses. Consequently, J607 gives higher values, which fail to include the friction losses. SAE J1349 is a newer standard which does specify various ways to include the engine's internal losses, and therefore presents a more accurate indication of engine power.