Healthy enough for tuning?

[bighorn466e]

I am putting together an International 4300 for use as an RV hauler and have been working to kill off all of the gremlins and collect some baseline data before turning things up. I've been able to work everything out but one issue and am hoping for a bit of help in determining if I'm chasing a phantom.

The 4300 was originally a VACIS mobile xray system used at the port. This means that it spent the majority of its life moving back and forth at <5mph powering a 5kw underhood generator. On my initial test drive the vehicle felt like it hit a bit of a power cliff after driving for 10ish mins. I negotiated with the seller to drop the vehicle off at a local international dealer and they diagnosed it as having low boost (19psi) and a bad turbo. Seemed like an easy fix so I purchased the vehicle and pulled the turbo only to realize that not only the turbo but the entire engine seemed to be a fairly recent Navistar "Renewed" unit. After confirming with a turbo shop that there was nothing wrong with the unit I bolted everything back up and changed the fluids/filters with no change.

I purchased a grandview rp1210 cable and did quite a bit of datalogging with the Navistar software before realizing that the brass bodied Intake air sensor had no underhood airflow on the outside of the sensor with the generator in front of it and was recording IAT's well over 150*. I unscrewed the sensor, draped it into the airbox so the entire sensor was in the airstream being measured and that issue was "solved" and the truck seemed to be running great.

I pulled the xray body, installed a flatbed and and used the truck to haul the camper (36' 5th wheel ~12k lbs) to a race in early January and then in mid march. On the way to the race in January temps were in the 60's and below and I didn't notice any problems. A few weeks ago however while loaded with the camper I once again had an issue where when the truck was "hot" the turbo sounded different while spinning up and the truck was struggling to do 60mph when it previously would pull >65mph.

When "hot and misbehaving" the truck has ICP within half a percent of requested, coolant temps at ~196, oil temp ~217, IAT ~105 with ICP's around 3200 and pulsewidths around 2400. If there was defueling occurring I'd assume that the ICP, Pulsewidth, or Boost values would be different between the cooler runs where the butt dyno suggests things are healthier and the hotter runs where something "feels" off but I can't find data to back that up. The only "smoking gun" of sorts I have is that in the attached datalog where things didn't seem right you can see the boost pressure drop from 20ish psi to 16ish psi right at 54mph. Given the consistency of the other parameters I'm not quite sure how to interpret this.

My outstanding question at this point is what I can or even should do to verify everything is healthy before turning things up. I have a sneaking suspicion that the servicemax software doesn't have the granularity to go much further.