i have a set of flowtech headers and y pipe and when you open the hood you can hear it rattle pretty bad on teh passenger side and at first i thought it might be a loose valve lifter but now when you accelerate you can hear it shake farther back and it rattle pretty bad and the hole time you accelerate from a stop. does it have anything to do with my exhaust beeing too close to the bottum of the car? when i put on my headers and y pipe i had to jack up the middle of the exhaust and rig it up so that it wont rub the ground. can anybody help me?

Check the Y pipe clearance around that corner near the front wheel.

Also check the tube that goes to your catalytic converter, it might be rattling against the y pipe.