I don't think that you can have too much heat when using a plate and tubes for water or exhaust gas. The stock configuration has the intake and exhaust manifolds literally bolted together.
The problem with a cold intake plenum is that fuel can fall out of suspension and pool on the floor of the manifold. Once it has pooled there it is no longer being metered by carb/injectors and can make it's way into the cylinders on its own (enriching the mixture) or continue to collect there (leaning the mixture).
Tuning mixture implies being in control of the mixture.
