Loosen the two locknuts that hold the cable to the bracket on intake manifold and adjust them so that the tension between the throttle cable bracket and the throttle rotor is taught, with maybe 1/2" deflection. Once you get it where you want it, look at the butterfly plate and verify that it closes completely when the throttle is not engaged. This would be a good time to clean out your throttle body with some intake cleaner if you haven't done so in a while.