I was wondering what, if any differences there are in the 99-0g intake manifolds. The difference in the Serial numbers are the last 2 letters. AA, AB, AC. I believe the AC is for the 05-06. I assume there were different manufactures but was wondering about differences. Does one company have a better quality part? Is there any flow characteristic changes? Or any other? I was hoping some one has some information on this. I was talking to Nick from Kolak performance and he was intriged but did not know. Any thoughts, old blue, ET?