Gaseous
I don't know how long you've had your Enstrom or what your bills look like, but I do know why some engineering companies won't have Enstroms in the hangar - because they're tired of explaining the bills to customers.
The Robinsons are derated to reduce engine wear, increase life and reduce maintenance bills.
As a side-effect, the derating improves safety because when a Robinson is operating at nominal maximum power it still has two or three inches of MAP and 30hp in the locker, which will get you out of trouble if you're prepared to scream the engine up to the level that Enstroms operate at all the time.
PS: Don't be in a hurry to give that spare engine away. You're gonna need it.