Sounds like a vacuum leak. The idle screw won't rev your car to 3000 RPMs normally. If you bury the idle screw and it still does it, you definitely have a vacuum leak.

Check hoses and also make sure they're all going to the right places. Spray a fuel source like carb cleaner all around the throttle body gaskets and intake manifold flange and see if it affects the idle speed (adding a fuel source to the vacuum leak). Avoid painted surfaces with that stuff. If it does affect the idle, you need to fix whatever is leaking.

Also, your engine is from a VX, what's your ECU and the rest of the chassis? Is that all VX stuff, too?