100% with what you're saying, however my driveway is straight and flat.
My tank was at half when I took the pics.
To my eyes ot does look nose high
I took another look at your pictures and the truck does look nose high, at least by what the wheel flares are showing. And if your on pretty level ground. Body parts can slightly vary by very little from truck to truck and how they sit. The truck cab/bed overall(roofline) should be level to the naked eye.
Curious and you may have mentioned, but is anything in your bed? That cover you have shouldn’t make a difference. Any other mods besides exhaust? Looks like the truck is squatting some.
Also get under the truck and look at the springs. Are they dead into the perch stop, meaning the end of the coil is up against it? Not common but I have seen them installed improperly. Sign of this is clunking noise. Just another thing to check.
Normally the shock reset routine isn’t needed after the install. But as mention, it could be a safe bet to run through it quickly.