Mike,
The You Tube video you were watching was an infomercial that was trying to sell you something that you do not need. The dyno test that they were showing was at the rear wheels, and not at the engine. If you take into consideration the loss in power through the transmission, intake restriction, exhaust back pressure, engine accessories (alternator, A/C and air compressors, and hydraulic pump), and final drive (differential), the engine being tested was probably producing spec horsepower and most importantly spec torque.
Any changes that you make in the programing of you engine to increase power will also increase the need for more air and cooling because of the excess heat generated by the engine in producing that power. Your engine is capable of producing more power, but like Dave said "at a cost". The C12 marine engine produces an excess of 700 HP, but it has water to water cooling and huge air intakes that your coach does not have. So unless you are willing to spend large sums of money, and a lot of time to correct a problem that you do not have, leave your ECM programing alone.
Fred,
You have a C 12, the most economical big block diesel used in RVs. Leave it alone, for the same reasons cited above.
Gerald