(defn transform-map [map funsmap]
  (reduce (fn [m key]
            (if (contains? m key)
              (assoc m key ((get funsmap key) (get map key)))
              m))
          map (keys funsmap)))

(transform-map {:x 1 :y 2}
               {:x #(* 20 %) :z #(* 10 %)})
gives
{:x 20, :y 2}