Ford Repair: 1999 Explorer Check Engine Light, upper intake manifold, air control valve

Question
I actually have 2 problems. The first is a check engine light. This is a 1999 Explorer XLT with 43,500 miles and has the V6 SOHC. The OBD-II shows that there is a vacum leak but does not specify where. None of the sensors have thrown a code. The vehicle is a hard starter when cold and outside air temps are down below 60 degrees.It runs rough and stalls out until it has warmed up. Also, fuel economy seems to have deteriorated.The check engine light reset one time then came back on and now won't reset. My local garage says the scan tool shows only that there is a vacum leak but they were unable to locate one. Any ideas for me to check? Have there been obscure leaks in the Explorer that are not common and most local garages wouldn't know about?
The second problem is how do I replace the bulb in the right side cruise controls? The left side is still lit up at night and the cruise control works fine but the lack of a light on the right side is a bit annoying. My Haynes manual (almost worthless) says nothing about this and my owners manual does not list the bulb type. If it's easy to replace I'll do it rather than pay a dealer way too much.
Any help you can give is greatly appreciated. Thanks in advance.

Answer
A common problem for Explorers is a vacuum leak between the upper and lower intake manifolds.  There are o-rings gaskets between the manifolds that go bad, the new o-rings have been redesigned, and should last longer.  Another common cause of an intermittent hard starting and poor idle concern is a bad Idle Air Control Valve (IAC). When starting the engine and when idling, the throttle plate is closed and the only air entering the engine is through the IAC. This is all controlled by the Powertrain Contol Module. It uses the IAC to allow a small amount of air to enter the engine for starting and to adjust idle speed. The IAC is mounted to the upper intake manifold with two small bolts, and has a small electrical connector on it. It is about two by four inches. It may be sticking, you can remove it (be careful, it may have a paper gasket) and clean it out with an Air Intake Cleaner. If this doesn't help, it may be failing and need replacing.

The light bulbs in the Speed Control Switches are not serviceable, the switches must be replaced if the bulbs are burned-out.