Your correct. First check your fuel pressure and volume, to make sure your getting adequate fuel supply. Often times a dirty filter can cause lean running. Next, you need to check to see if your engine linkages are set correctly "Linkage Tour". If the engine is in good tune you can try the linkage test above 2,000 rpms and then above 3500 rpms. If you find only the low range is lean (idle to 1700 rpms), then you can richen-up just this range by turning the knurled thumb screw on the back of the injection pump in a few clicks (clockwise sitting in the car) and make sure the engine is NOT running when you do this adjustment. If you find that the engine is running lean at all speed ranges you can make a whole injection system adjustment by turning the main IP rack screw or removing some shims under barometric compensator (easiest method). keep asking questions.