Saab engine error codes



My 04 Saab 95 2.3T has engine light on about 80% of the time - took it into dealer who found codes P1312, P1334 and, P1340 – they say it means I need new discharge module and new plugs – for $525! I really can’t feel any performance issues with car - sometimes hesitates when flooring it at a stop sign…what is discharge module? Can I get a local guy to do this for much cheaper? Thanks…