yet another exhaust question

[blackfox]

i am buying a set of longtubes and single chamber flows off a friend for 150, my friend has a similar set up but he has two straight pipes from the header back, instead of the H pipe, which i have. how much do those pipes cost? the straight ones

 

[blackfox]

oh and if you see this and can help- please post i really wanna get this done but i need a price range first

thanks