Idle Change, Injector Knock?

While idling there's a noticeable idle change that occurs occasionally. It's a 2015 KW T680 with a Cummins ISX that's deleted. I had a pickup that was deleted and the first tune on it was a bad tune and I learned what injector knocking sounds like. The sound my KW is making is similar. Sometimes it begins sounding like injector knocking randomly and idle fuel usage goes up about .3 gal/hour. Then after a few minutes it goes back to normal. Continuous cycle between normal and what sounds like injector knock. I'm just wondering if it it a sign of dirty or bad injectors or a sign that the tune on here is trash. Either way looking at big $$$ repair. What are some things that can be done to diagnose the injectors? Someone also told me that this model Cummins sometimes does some weird stuff when injectors are dirty. The thing that caught my attention is they said the coolant fluctuates when injectors are clogged/dirty. What's the link between injectors and coolant? Why would clogged/dirty injectors cause coolant to do anything? My coolant absolutely fluctuates frequently since I get low coolant warning all the time. Dealer said it's likely the wiring since I've replaced the reservoir and sensor. Couldn't fine any breaks in the wire so I just live with the warning. Based on what this person told me about the injectors it may all be related. I've also noticed a significant decrease in fuel economy lately. It's all stacking up, just trying to put my finger on it.

 

Yeah it's not the compressor. That knock is similar but this knock is definitely injector knock. It sounds almost exactly like it did on my 6.7 cummins. Except the 6.7 had it all the time.

 

Alright. I've got a trustworthy place to take it to to get some accurate results. What does an injector replacement or cleaning usually cost? Rough estimate.

 

OK thanks. I'll post what is discovered around the 14th