Everyone who perform Tahajjud supposed to ask forgiving to Allah. If I may reveal what my Tahajjud Dua is, it will be for my parents (all), my children, people who hate me, and people I love. The one I love, included too. I ask Allah to forgive their sins, free them from grave nor hell torture. So.. don't think that I ask for Dunya when I do Tahajjud. I've pray for your grave already.