downpipe question?

Hey all i have a very newb question but i did search and there wasnt many post regarding the specific question i have. so here goes what is the difference between the wastegate dump tube and a downpipe? from looking at the AAI install instructions i have it appears to me that its the same thing? and if they are seperate pieces do i need to get a Y pipe so that the wastegate dump tube can be routed in there also?

the down pipe is the piece that connect both banks (exhaust from both sides of your engine) together and into the cat.

you will want to do something like this..

http://memimage.cardomain.net/member_images/12/web/360000-360999/360180_70_full.jpg

notice the wastegate dump tube is plumbed back into the exhaust

What is the other pipe that is there? the one next to the wastegate? it seems to go no where?

http://memimage.cardomain.net/member_images/12/web/360000-360999/360180_70_full.jpg