i recently did an exhaust upgrade and am running a straight pipe with a custom pick up tube. i noticed a tube just behind it aux intake tube where im pretty sure the old pick up tube ran to, now everything is blocked of like it should be but that tube. when the car is running it sucks in air and it seems to effect the idle a little bit. the car works either way but seems to idle higher with it capped off.

what am i supposed to do with it? im hoping to get pix up real soon of exactly what im talking about.