FM7 ECU Swap (more power?)

Hello everyone! This is an odd one, the vehicle I am asking questions for is actually a bus, a Volvo B7R. However, since online knowledge of buses is extremely limited, we'll pretend it is a Volvo FM7 (as they share engines and other electrical similarities).

My question is, the engine in my *FM7* is a Volvo D7C250. What i would like to know is, if I change the engine ECU to one from a D7C290, will the vehicle function and give me the rated 290bhp? Or am I naive and the engines are in some way different, or the power rating of the engine is controlled by vehicle ECU or something else more complicated.

The vehicle is a 2006 model year, so it has the later dashboard with the big orange/brown screen between the dials like your guys trucks (if this detail is important)

Thanks everybody!