3361 active with 2387 inactive

[tow440]

Hi All
First post here.. fire department fleet mechanic, I have a 2014 isx 20k miles that keeps throwing a 3361 intake pressure code and usually it always has the 2387 vgt actuator code inactive when i read them. happens intermittently sometime can be weeks in between, cant duplicate it. changed the pressure sensor and also have put a vgt on it.. dealer says could be a seal in the turbo causing the issue. just wondering if anyone has seen this before. I did have to replace the dpf as it idles a lot and mostly short trips and apparently didn't get regened.truck runs great until the code sets then ends up on the side of the road. sometimes it will make it a few miles, other time throw it before it gets out of the driveway. truck is a 3500 gallon water tanker. any info would be great. i did replace the exhaust pressure sensor just for fun as i know sometimes they can fail and not set codes and it actually hasn't acted up since, coincidence?

thanks
dave