forgive my ignorance, but i've recently decided to change to a metal intake pipe from my stock rubber one that's connected to my blitz pod... but i noticed there 's a hard plastic 'chamber' connected to the stock pipe a little way back from the throttle body... could somebody tell me what this is? i've got a D16Y1 if it helps...

and also, how much should i expect to spend if i go an exhaust place and ask them to make me a custom pipe?