I may be a rookie when it comes to old Macks and I find myself here asking for help and I get it! But im very familiar with the 7.3 powerstroke and the 6.9/7.3idi. I have several of each and run them everyday for work and for play.
The 7.3 psd is capable of mileage and engine hours that aren't seen on many other medium duty engine. If it wants it straight piped, it won't hurt it....it sounds "good" for a while, then he'll grow up after a couple years of it. They are a HUEI engine, which is fine....just a little different to figure out when there's problems and they do not tolerate dirty oil for long periods of time. He's gotta keep his oil changed on time. Keep the EGT's in check. I could go on and on. ECM tuning goes a LONG ways for performance. I only run a mild tune on them....im not out to win races....cause it won't. But a mild tune wakes it up just enough for me. Drive accordingly. Keep it maintained, and be happy and make money.
Yes, the 7.3psd has a handful of idiosyncrasies that can cause a fella to pull his hair out trying to figure out runability issues. But once they are understood and the quirks are dealt with, they are very good.
Full Floater's post in Striaght pipping a Ford F-450, with a 7.3L was marked as the answer