[Lighthorse]

Val,

The ai empires that counter attacked me were the Centauri Republic Republic(could you remove the second republic from the Centauri name please) and the Drazi Freeholds. They both were using general weapons(particle cannons and plamsa point defence), ecm, combat sensors, elite ground units and fighters-particle gun II with excort carriers. Normally the AI would only used matter gun and other pea shooters. Plus by increasing the speed of they fighters from 1 to 3 have increase the fighters effective.
You should also have the ai build large amounts of ship yards at their homeworld, thus increase their ship building capicity. Allot a quarter of yards to planet defense/fighter/mines, another quarter to colony ship/transports ships and the Last half for warships.