I talked to my builder about using the GT500 TB. He said that you cannot use the piece because it uses bronze gears that bind up under the extreme heat produced by the KB. This was the problem with the KB prototype. Remember, this was also using a 2.6H which are supposed to be alittle cooler (relatively of course) and not a 2.4 or 2.6L. They had to switch to the BBK because they use plastic gears that wont bind. James @ KB knows of the situation but I am unaware of what they are doing to correct it. Again, this is only the situation for KB's