-the throtle valve rotates around it's center(left-right) and the lower gap changes in size
This make me wonder if the slide has not been placed correctly on its alignment pin.
If in the correct position you should not be able to rotate the slide.
This will effectively hold it open causing it to rev like mad and not respond to air screw.
Remove the top cover and rotate the slide till it finds the alignment pin.
If set correctly the slides cutaway will be on the intake (air filter side)