Through the recent book fair being held in Expo Centre, Karachi, I came to know about you and the books you wrote on Islam. I read two books of yours and found your findings very much correct and reformative. I not only appreciate but also admire your approach. I have a question which I want to ask from you and I know you will answer it in the light of Quran and the Sunnah.
First of all, I want to tell you something which is related to my question. The Imam of the Masjid where I used to go for the salah is often engaged in chanting Allāhū (name of God) all the time and keeps on shaking his head. He also asks his followers to do the same. According to my knowledge about my religion, this is not proved through the whole life of our beloved Holy Prophet (sws), the four Caliphs and the general companions (sahabah-i karam). Further, the Prophet (sws) said: "He who innovates something in this matter of ours that is not of it, will have it rejected." (Transmitted by Al Bukhari & Muslim).
Now, my question is: Can I perform the salah behind this Imam? Is it allowed to follow the Imam? What shall I do?
As long as a person is considered to be a Muslim and prays the way Muslims pray and is not famous for leading a life full of sins, one can follow him in prayers. Wrong beliefs and wrong practices do not disqualify a person from being Imam in prayers unless the wrong belief is so extreme that takes the person out of the fold of Islam or the practice is so wrong that totally changes the way the person prays.
The practice you mentioned, as you said, has no basis in Islam and should not be followed as a religious practice.