I thought the same think, If IAC and TPS are good then it's most likely a vacuum leak. I think those engines are prone to leaking manifold gaskets IIRC.
I thought I found the vacuum leak when I took off the throttle body and found the TB to intake gasket was torn, but after replacing it the idle was high still. I'll take a look at the bolts and gasket too.
An easy way to check for vacuum leaks is spray all around the hoses and intake gaskets or where you suspect a leak with a can of brake clean or carb clean. The engine will start to die when you spray where the leak is. That is the easiest way to check for vacuum leaks. If feels sluggish also check fuel filter if has one on it. Clean your MAF sensor too. Sometimes the wires in the sensor get crap on them. Just clean it out really well with brake clean and becareful not to break the wires in the sensor. The wires I am talking about are in the intake tube not electrical plugs too lol. Hope helps out