I am making an intake and need a straight piece.......

ABS would be better than PVC theoretically, as when it (PVC) is subjected to extreme heat and melts produces a toxic chemical. However, the heat this pipe would be subjected to would not be that severe.....the battery can handle it so the PVC should be fine.

Acrylonitrile-Butadiene-Styrene (ABS) - will not produce a toxic chemical when melted, but is just as hard to find and offers less bends/options for an application

Either is fine, the toxic chemical given off is not dangerous unless you would be locked in your garage when the car is on fire, then again you may have other issues like getting out of the garage.