Ford Repair: Idle Speed on 2001 Ford Ranger 4 cylinder, vacuum lines, pcv valve

Question
I recently took my Ranger in for a it's 60K service. It was running fine before I took it in, and the shop is one I have been going to for a long time. Some of the things they did was to flush the throttle body, changed the PCV valve, flushed the radiator etc (normal stuff).
After I got the truck back, the idle was really doing crazy stuff. It would rev up when I took my foot of the gas and pushed in the clutch.
I took it back immediately, and they ended up changing out the PCV valve to a factory one instead of the aftermarket one they had put in. This seemed to help a bit, but it still seems to be running strange. When I push in the clutch and take my foot of the gas the idle only drops slowly to about 1400rpm (while I am still coasting). When I come to a full complete stop, then the idle will drop to about 800rpm and seem to idle fine. The guy at the shop said that it may be the battery since it was marginal when load tested (which I thought was a load of bull).
Before I take it back into them yet again I would like to find out what others think.
Thanks
Zack

Answer
A low battery will trick out you're computer.I had a car once that when I replaced the battery in it,for about two drive cycles it would die at traffic lights and stop signs.You want to talk about frustrating.It was a Chevrolet(lol).Check the vacuum lines around the PCV and see if any of them are broken,or knocked off.