Lean condition raises the burn temperature, so yes, anything will heat up more. Anyway, as someone else stated, under low load, this usually isn't a real problem. The only thing to watch out for is the cats, if you still have some ... IIRC, cat protection will add additional fuel when it kicks in to lower exhaust temperatures ...
Well, I sincerely hope not! J/Klean cruise actually makes, don't think it's going to turn a 6.0L in to a Honda Civic!