No Sir I do not have my own shop, nor do I work at one, but I do have one thing working to my advantage, common sense, which it seems your dealership does not have. Now, my favorite technician of all time, has got to be the Diesel Tech at University Ford in Durham, NC. I know him, I know his mother (haha), and I know a few of his friends. He has always gotten things fixed on the first try as far as I know. I am sure that there are much better techs. between here and there, but I can put you in contact with him, and let you explain to him, and get his opinion on the matter.
Another question. as you say it's a "navistar" The engine is not a light blue is it?
Anyway, Post the vin# here, (Do we have an OASIS forum??) and if we dont, post it here, and I can call him and get him to e-mail it to me.