i recently did both power valves and swirls valves while at it,replaced the old screws with new ones. got them 24 cents per screw from ace hardware. size and thread pattern is m3x.50 10mm length, then used the high strength red loctite so i would have a peace of mind those screws wont come out. i would recommend to change the intake manifold gasket, pcv,valve cover, spark plug seal, emission valve cover hose that connects both valve cover since they are plastic and get brittle, while u work down there because everything has easy access while the intake manifold is out. do it once and do it right the first time.
as the torque for the intake manifold. i did all 12mm bolts and nuts at 20lbs.