What is this B pipe? does it go with the Y pipe under the car? Or is it pretty much the same as the Y Pipe but without as much exhaust freedom? If they work together under the car, can I go with one and not the other?
HELP ME PLEASE!!!!!

 

B pipe goes from the main cat to the muffler... y pipe is from front pre-cat to main cat. You need (have) both on your car.