Idle problem
 

When I start my 2003 WRX it goes to 2.5 thousand RPMS. It stays at 2.5 for about 7 seconds then goes down. After it goes down my check engine light comes on. But if I give it some gas and take it to 3 thousand my check engine light doesn't come on. Has anyone else had this problem? If so how did you fix it? I have tried cleaning the idle air control valve already.

Have you checked what the code is?

Sounds like your throttle cable is too tight, Adjust it. Clear the code and your idle should be 500-700. Make sure you don't adjust it too loose or you will have a hesitation. Also could be a vacuum leak post throttle body. Done any work to the manifold recently? Lines/gaskets?

It is P1507

I have only replaced the gasket the idle air control valve sits on.

Yep thats the code. Like I said check the throttle cables for proper adjustment and binding. Any post t/b vacuum hoses appear to be cracked?

Also worth checking the wire that goes to your power steering pump for a loose/bad connection. If you have a code reader that can see the neutral safety switch turn on a off that's worth a check.

If you tap on the valve with a screw driver the idle change at all?