Apparently the new 2013 emission ISX engines haven't been plagued with as many problems as it's predecessor. We bought a 2014 388 with an ISX 550 and it has been problem free thus far. That being said, in a year and a half I've only accumulated 17,000 km....so not much of a test. I'm averaging around 60L/100km pulling Super B's.....lot's of stops and starts on a 125km round trip. Power is OK, but 600 would be better......