i replaced the stock airbox with a ebay k&n type air filter and i was wondering if it matters what position that big airflow meter it connects to is in. mine is pretty much vertical. my car runs like complete **** but it was running real shitty even before i replaced the airbox.

 

with the flapper door you want it pretty much horizontal (so that the air enters horizontally). Otherwise the door hangs open slightly or gives incorrect readings due to whatever way gravity is pulling on it.

 

it should be vertical and the top has to be facing up, can't rotate it.