if it's timid nature, you may as well give it Choice Specs or give it nasty plot.
Porygon @ Choice Specs
Timid Nature
252 SP ATK/252 SPD/4 HP
Ability: Adaptability
-Thunderbolt
-Ice Beam
-Tri-Attack/Psychic/Dark Pulse
-Tri-Attack/Hyperbeam/Hidden Power Fighting
nice.
Porygon @ Leftovers/Chople Berry/Lum Berry
Timid Nature
252 SPD/196 HP/60 SP ATK
Ability: Download
-Ice Beam
-Thunderbolt
-Nasty Plot
-Substitute/Thunderwave/HP Fighting
nice. the strategy is that you basically bring it in against something like skarmory or tangrowth or some other defensive poke with below-average special defense, use substitute while they switch out (or paralyze the switch in or just use nasty plot), and then you have a free turn to use nasty plot. you may even be given more time for another nasty plot depending on what they switch in.