Nitrous was known, but they could not have safely used it. The tanks available then could not have been jettisoned and the amount of additional fuel used while under nitrous power and hauling the heavy bottles afterwards would have meant failure. They had to remove most of the B-25s’ guns and the remaining few guns had almost no ammo aboard - that’s how desperately they had stripped the aircraft to get it to complete the mission. Given that no few of them barely made the Chinese coast, it turned out the margin really was so thin that a few pounds might have made the difference.
Same thing for water injection, which was also known at the time and was more common. And then there’s the reliability aspect.
WOW! FR is a source of knowledge like no other.
They probably considered it back then but the trade offs weren’t worth the risks. I thought perhaps the added power might have enabled them to carry more fuel off the deck, more than the extra that might have been consumed while using the nitrous and the engines were somewhat expendable as long as they survived the launch off the deck and trip.