In first gear when i rev up to 3 to 4 grand and hold it there and when i do the 1'st to 2nd shift im hearing a rattle like buzzing sound. At first i thought it was the heat shield but it seamed pretty tight. I was thinking it could possibly be a rattle in the cat or a problem with my clutch-flywheel assembly. Can any one help me out on this, does it sound familar?