Cook the bulgur wheat according to package instructions, then spread it on a platter to cool and fluff it with a fork.While the bulgur cools, soak the red onion in cool water for 10 minutes, then drain thoroughly.Slice the cucumbers, chop parsley and mint, chop pistachios, drain the chickpeas, and crumble the feta.In a large bowl, combine the cooled bulgur, cucumbers, parsley, mint, chickpeas, red onion, and pistachios.Add lemon juice, olive oil, salt, and pepper to the bowl, followed by the crumbled feta.Toss everything gently until well mixed. Taste and adjust seasoning, lemon juice, or olive oil as needed.Serve chilled or at room temperature, garnished with extra feta.