The problem is when I am either at 1500 rpm or 3000 I get this rattling from under the car. Is it my head shields or something else and would could I do to fix it.
Also when I am in first or second gear and I bring the rpm's up to about 3500 I hear this weird buzzing sound. Could it possibly be the muffler (bought off ebay), or could if maybe be my valves floating?

 

the first rattle is you heat shield. the second "buzz" you described is most likely your a-pipe.

 

Would it hurt anything if I took the heat shield(s) off?
I am not too familiar with what the a-pipe is, and how can I fix it/buzzing sound?

 

i've had two cars do this, one i took the bottom of the heat shield off and it fixed it, the other car i tried everything, even new muffler and it didn't fix it. I finally decided it was the resinator, and i just dealt with it 'til i was ready for full exhaust.

 

the cheapest way to fix the a-pipe is to find one at a junk yard and hope it doesnt have the same problem, or by a header.

 

Use a hose clamp to resecure the heat shield.