We do the I-70 tunnels all the time. Screaming going up and screaming going down. Tow/haul is great for the steeps. If you need to slow down some more, do it a little at a time. Use the brakes to get you 5-10 mph below what is comfortable - don't worry about doing 30-40 (or even less if you have to), and then let the coach speed up if it wants to. Then slow down again. Don't ride the brakes trying to hold a constant speed.
West side of the tunnels and Vail Pass are a lot steeper than the east sides, so we take them at 40-45 and slower for some turns. Going up we are usually 40-45 all the way.
2017 Thor ACE 30.1
2017 Jeep Cherokee Trailhawk
Roadmaster Falcon All Terrain
RVi Brake 3