Not uncommon for headers to get red hot, for mounts that use engine and blower exhaust to heat solution a certain amount of back pressure on the engine exhaust manifolds is normal for prochem/SS models. They are cerakoting parts now for improved heat performance and longevity. While a motor can handle a little back pressure, to much will remove a couple thousand hours off the motors lifespan. A free flowing exhaust doesn't trap the heat nearly the same. We have a 15 year old Kohler with 6000+ hours on it that has had back pressure it's entire lifespan... a little is ok. Carbon buildup on the valves and pistons is normal, pull the jugs after 3k hours, knock it off, new head gaskets and lifters and reassemble. 3 hour job with very few bad words lol