Welcome to the forum, the Ambassador is a really nice coach. While I don't know own one yet (about to order a Dip 43dfdt), as for the maxxforce 10 engine there doesn't seem to be a lot of problems with them, at least any that have been reported.
When we test drove the Diplomat with the MF10 and 405 hp, I felt that it was pretty much equal to the cummns ISL in perfprormance.
The MF10 with 350hp that comes in the Ambassador should preform fairly equally with the Cummins ISC engine that is commonly used in that level of coach. It should have no problem moving the Ambassador down the road and up the hils.