What does code P1294 refer to specifically? The pump, filter, lines, etc.

Have you actually had this diagnosed, or have simply asked for suggestions? There are numerous items that can cause this code to set, and you may sift through many ideas before actually finding the culprit. A quick check of the definition and criteria of setting this code tells me, basically, it's a code that tells you what you already know. To paraphrase the code description reveals the the ECM detects that the idle speed is not within it's expected range, and since you mention that the idle is fairly terrible, the code is almost worthless. I say almost worthless because along with the code being stored there should be information stored as to the conditions the vehicle was under during the problem event, or freeze frame data as we call it. It sounds to me like you need to find a competent automotive repair facility and have them diagnose the problem, thus ruling out all of the thoughts and ideas.