On the "lose" issue...tire pressure will affect the handling a lot. If the coach is on a dealer lot, chances are the pressure is too high (no stuff for added weight). If the dealer would be willing to lower the pressure by 10-15 psi and then you can test drive again, you probably would feel a difference. Tire air pressure should be set based on the weight of the coach and contents.
340 hp will be okay depending on where you live or plan to travel. We live in the hills of western PA and no matter which way we go, it is either up or down! ARGH! One of the main criteria for us when we were coach shopping was a 400 HP diesel. Our coach is also a 38 footer.
Good luck with your search.