I keep getting the PO171 and occasionally the PO174 codes. I have replaced my PCV valve and ALL the lines, including the 90 degree boot on the back of the engine. I have put clamps on all the connections. I used starting fluid to spray when it runs rough and it keeps coming back to the little hose connector that is embedded in the hub that the throttle body is mounted to. Could this plastic connector that one of my PCV lines connects to have some sort of leak? If so, do I need to replace the entire piece and if so, how difficult of a job will that be? It doesn't "look" too difficult. Also, any idea on how much that piece will cost?