No problem.
Turbos get up to 1000F-1500F when driving, with 1500F probably closer to the upper end (towing uphill or something) so gotta have the heat shields.
If it's anything like this video (not my video):
It's normal. My Tacoma makes those same sounds if you shut it off once its up to temp. Even more so after a long freeway drive. Turbos get hot, gotta have a lot of heat shields. Those also get hot and then cool off. My Subaru also makes exactly...
I think you're hearing heat shields etc metal contracting after the engine was running (hot). My Tacoma and WRX hatchback do the same thing. Usually on turbo vehicles the downpipe, turbo and sometimes cats are covered with heatshields and they get real hot, and then contract, so you get...
As far as aftermarket parts go, a skidplate doesn't seem like a big deal. The dealership should be happy you're there to begin with because oil changes are one of their big winners revenue wise.
I'm getting CBI front and rear plates (one day haha, ordered about 2 weeks ago)... and I'll be going...
Same spec, SR DCSB 4x4, stock wheels and tires, air dam is gone and I added Rokblokz mudflaps (thought they may decrease mpg), no roof rack or bed cover... I'm seeing those numbers too, 20-22 urban driving, easily 25-27 for freeway trips.
When I get more offroad friendly tires I am going to go...