New Owner Cleaning EGR Passages

I'm new here having bought a 2013 Prius Three about 3 weeks ago. I am the DIY sort with 50+ years experience wrenching on my cars, boats, motorcycles but I know I don't know it all and I really appreciate the plentiful resources here at Priuschat. I am sure there are many helpful owners here but a shoutout today for @Mendel Leisk. The links in his signature have already helped me to familiarize common service tasks. My new to me car has 189,xxx miles and somewhat of a full service history. I have records from day 1 and I am the third owner. The car was serviced primarily at two Toyota dealers up until the day it was sold wholesale. It runs great and has no codes stored. In about 900 miles I cannot discern any changes in the coolant or engine oil levels. Happy about that. Runs smooth and transitions back and forth between engine and EV operations smoothly. This morning I pulled off the EGR tube to see the type and amount of carbon buildup the rebreather system has at 189K. There is no record the EGR valve and chamber have been cleaned to date and I gather that is an important item to keep clean to help avoid head gasket problems. I was pleased to see the soot in the pipe, outlet of the intake manifold, and inlet of the EGR was absolutely dry. The pipe and EGR inlet had the barest minimum of soot, very clean but I used some flexible brass brushes and brake cleaner to clean these passages out. Now the inlet manifold had more but still dry and sooty. There was about 1/8" build-up on the inside of the intake manifold outlet. I did not pull the manifold today but connected a flexible 3/8 ID vinyl hose to a handheld vacuum cleaner and used the hose round and round and in and out to scrape the surfaces clean for the two or three inches that are accessible. I captured all the soot I removed from the tube and manifold and it came to less than 1/2 teaspoon (pictured). It's much like minute bits of charcoal. No oiliness what so ever. What can I expect the inside of the EGR chamber/cooler to look like based on the pipe and manifold?