You might consider going with a little older wheeled machine in exchange for some more HP. If you search Google for Morbark D52SPH or Bandit 2450, those are a couple machines that offer pretty decent bang for the buck.
Sorry it took so long but the notification from this site went to my junk folder. I'll check it out! Is that the number off of the tongue of the machine? I have never ran across one with a letter at the end. The last 5 digits are the most important and should start with a 24. (i.e. 24143)
Do you know your machine serial number? I could pull the build sheet and see how it was configured, it is possible that the autofeed valve you speak of it letting some of the flow go back to tank or something.
If I remember right the tube from the air cleaner to the turbo rubs against the alternator bracket at times on those engines. I've talked to a couple of guys that have blown them up from all of the dirt getting into the turbo. It would be something to keep an eye on anyway!
We have a nice 2015 Bandit 2550 with the 44hp Kubota on it. I haven't used it but I know the Bandit 2450 Kubota diesels were awesome machines. I would say in that HP range, anything with that V1505 Kubota on it would be a solid choice.