jtnak

I've seen a lot of post on this code. I've got a 98 GS 300, checked all the vacuum lines, new gas cap and checked both vsv valves. I put power to both vsv valve and they switch on, does anyone know if they can still be defective because of resistance? Any other suggestions that I might check before I do a smoke check? I've reset the CEL, but come back after about 20 miles.