I suspect it's a N52MHP where the "M" stands for magic, you almost certainly have one of these engines when you simply know it has 300hp, mainly because you've done all the work on it yourself, and you know it's faster than some of the others you've seen on the internet.
Looks like a reasonable car with a questionable history, if you got away with a new engine and/or potentially some electronics there could be some value in it. I suspect however the current owner knows it's not economical to repair.