Is deliberately mispronouncing words while reciting the Qur’an, such as saying “wa-tookal” instead of “wa-tawakkal,” considered major disbelief (kufr akbar)?

Deliberately adding a letter to the Quran is considered a grave and forbidden error (laḥn jalī). Qadi Iyad reported a consensus (ijma') that whoever does so intentionally is a disbeliever (kafir), because the Quran, recited and written in the mushafs, is the word of Allah and His revealed revelation. Therefore, whoever intentionally removes a letter from it, or alters it, or adds a letter to it that is not part of it, is a disbeliever. However, whoever does so out of ignorance is excused due to their ignorance. Reporting this error for a good purpose, such as correction or notification, carries no sin.