I'm sure you know this Rich, but don't install combustion air according to code and walk away without testing. Make sure it is actually working. ASHRAE found that passive combustion air intakes don't always work. Fan powered combustion air is the best.
Absolutely, I should have included this fact you point out. They tried to fix the problems with the 1 foot off the ground design. I can't stand atmospheric systems, period. Being in Ohio I'm so thankful that everything will be 95% or higher after May 15th, 2013 which means a sealed combustion.