ISX 600: Trouble in paradise

[Rocky]

Owner operator here. Almost two years ago I bought a low mileage (180k) Kenworth with a 2015 ISX 600. It was a single owner southern truck that had not once seen the snow and had just crossed the threshold of being under any kind of factory warranty. It's a beautiful truck and I got a great deal on it due to the age and therefore lack of warranty. I had one obvious plan in mind. The truck was a perfect candidate for "weight loss" surgery. I hated the idea of choking the motor with exhaust and being a W900; sounding like a pick-up truck.

I of course spent money (twice actually) to help in this regard and it has served me and my family well for the past nearly 200k miles. Until recently.

I've always known something wasn't quite right because with both the different shop "tunes", my truck sounds like a fighter jet about to take off when idling. The boost sits around 1.5 PSI. I am also lucky to see 5+ mpg loaded or 6 mpg empty; although it was not much better before surgery. So I lost what fuel economy I did have and if anything; as well as some performance. It is built for 100k+ hauling and has a 3:73 rear end with 600 factory hp, so it has plenty of power. Fuel economy isn't exactly its purpose .

A month ago the EGR cooler up pipe snapped near the cooler, so I replaced it. The next load out, the boot connected to it split. I replaced it. I've noticed over the past few weeks that my oil temperature is getting awfully close to the 250 f mark. I run full synthetic so I'm not concerned about oil damage.

This month I've run an overhead and performed a cylinder test via Cummings Insite trying to track down a vibration or "ruff" idle. I used the Rawze method of idling the motor with a single cylinder and repeating for all six. All cylinders “fire” and sound similar. I have a new dampener, IMAP, oil temp, and oil pressure sensors waiting at the house to install on my next home time.

What is my next theoretical step? Obtain CT and adjust variables based on recommendations? Who's? ISX15 parameters? The old "If you want it done right..." saying is truer more now than ever these days and I am running low on money and options in the current “climate”. Originally I thought "let the guys who do it everyday take care of it". How naïve of me.