Noise after clutch replaced about 1000 miles ago---37,000 mi.

What is your question?

I have a sound that is a rattle from under the car ever since the Clutch was replaced. I have Stillen pipes from manifold back- non factory, and the sho said it was the baffles in the exhaust make this noise? The said they could od nothing about it....... Problem is very noticeable when I idle in neutral