Hi, my LB7 was hard to start and had a rough idle, then i saw that there was a wet spot of fresh diesel around the drain valve on the right side of the alternator, there's a schrader valve inside that was not sealing compleatly, and this line (and any other fuel line on the feed-side) is a suction line and it was drawing air through the drain valve. it's worth a check.

Edit: sorry DmaxMaverick that i didn't saw that you already had mentioned the valve in your reply.. i was a bit too fast..