171 code back again

I had 171, 303, 301, and 401 codes in my 2000 Windstar. I replaced the isolator bolts, plenum gaskets, and cleaned the egr ports. It ran much better. It still has a slight miss at low speed and I got a 171 code back. I suspect a vacuum leak but I can't seem to find it. The heater controls aren't completely functional. Is that a clue? Does anyone have an idea what to check for or where to look?

Need to perform a smoke test to pinpoint unwanted vacuum leaks, see http://www.automotiveforums.com/vbulletin/showthread.php?t=1061642

Thanks. I'll give it a go.

The only leak I found was the EGR solenoid. It was a minor leak. Is this normal?

It sounds like you found the problem!