The jump in idle comes from the computer. It's the same mechanism that makes your idle jump when you turn the air conditioning on.
As for your high idle, I agree with the previous poster that it probably is a result of you not opening up the hole in the intake manifold. I don't see the point in putting on a 4.0 TB if you don't open up the intake. You won't flow any more air (which is the whole point of the swap). More airflow = more HP.
“The test of the machine is the satisfaction it gives you. There isn't any other test. If the machine produces tranquility it's right. If it disturbs you it's wrong until either the machine or your mind is changed.” ― Robert M. Pirsig, Zen And The Art Of Motorcycle Maintenance: An Inquiry Into Values