Help with my dune buggy 3.1 multiport V6?

The black plastic line is your PCV line. If there are more than 50000 miles on this engine chances are your problem is caused by the throttle position sensor. It is mounted on the end of the throttle shaft, opposite the throttle cable. They spend most of their lives in one little area of the potentiometer and the carbon wears off, causing screwy resistance readings just off idle. Don't forget to disconnect the battery and reset the computer after you change a sensor. Hope this helps.