How much should the imam recite in Taraweeh, and the ruling on singling out Soorat al-Ikhlaas to recite in the second rak‘ah
Question

What is the ruling on always reciting Soorat al-Ikhlaas in the second rak‘ah of every Taraweeh prayer? May Allah reward you with good.
Praise be to Allah.With regard to the way in which the Prophet (blessings and peace of Allah be upon him) offer the night prayers (qiyaam), ‘Aa’ishah (may Allah be pleased with her) described it in two words: Long and beautiful. She said: And do not ask how long and how beautiful they were. Agreed upon. As for the practice of his Companions (may Allah be pleased with them) and those who followed them in truth, it was similar to his practice. The night prayer [in Ramadan] is called Taraweeh because they used to rest (yartaahoona) after every four rak‘ahs, because they were striving so hard in qiyaam. We are amazed by those who become tired from offering salaat al-qiyaam nowadays, not from the length of standing, bowing and prostrating, but from how fast they move up and down in their prayers!
Everyone who knows the condition of those who recite Soorat al-Ikhlaas in the second rak‘ah, and also knows what the practice of the Prophet (blessings and peace of Allah be upon him) was in praying qiyaam, will be certain that those imams are going against the practice of the Prophet (blessings and peace of Allah be upon him) and will be certain that what they are doing is not permissible, because the imams should recite of the Qur’an whatever they are able to do at a moderate pace, with deliberation and without rushing. They should not race one another to see which of them will finish first, or make their recitation a mockery of the Book of Allah, whereby they recite and stop at a point where the meaning is incomplete, or they recite so quickly that it turns the prayer into a travesty and a mockery of the Book of Allah.
Maymoon ibn Mihraan (may Allah have mercy on him) said, I remember when, if the reciter recited fifty verses, people would say that his prayer was not long; and I remember when the reciters in Ramadan would recite an entire story, whether it was short or long. But now, I feel horrified when one of them recites “And when it is said to them, ‘Do not cause corruption on the earth,’ they say, ‘We are but reformers’” [al-Baqarah 2:11], then in the second rak‘ah, after al-Faatihah he recites: “Unquestionably, it is they who are the corrupters” [al-Baqarah 2:12]. [The problem here is that he is breaking up the recitation in a manner that is inappropriate and pays no attention to the meaning of the passage being recited]
Mukhtasar Qiyaam al-Layl by Muhammad ibn Nasr al-Marwazi, p. 224.
The scholars of the Permanent Committee were asked:
There are some imams of mosques who recite long or medium soorahs in the first rak‘ah of Taraweeh, and in the second rak‘ah they recite Soorat al-Ikhlaas after al-Faatihah, and they do this all the time. Is this action permissible? In addition to that, after every four rak‘ahs they recite a du‘aa’ together, such as saying:  “Allaahumma innaka ‘afuwwun tuhibb al-‘afwa fa‘fu ‘anni (O Allah, You are forgiving and You love forgiveness, so forgive me).” What is your opinion on what they do?
They replied:
The best in Taraweeh prayer is to start from the beginning of the Qur’an and continue until they complete it at the end of the month, as the Sahaabah (may Allah be pleased with them) used to do that. If it is limited to reciting some of the Qur’an, that is permissible, but [the imam] should not single out some particular soorahs and only recite them. It is also not permissible to recite du‘aa’ together after every four rak‘ahs, because this is an innovation for which there is no evidence in the Qur’an or Sunnah.
Shaykh ‘Abd al-‘Azeez ibn Baaz, Shaykh ‘Abd al-‘Azeez Aal ash-Shaykh, Shaykh ‘Abdullah ibn Ghadyaan, Shaykh Saalih al-Fawzaan, Shaykh Bakr Abu Zayd.
Fataawa al-Lajnah ad-Daa’imah, vol. 2, 6/84, 85.
Shaykh ‘Umar Sulayman al-Ashqar (may Allah have mercy on him) was asked:
What is the ruling on persisting in reciting Soorat al-Ikhlaas in the second rak‘ah of Taraweeh prayer?
He replied:
Persisting in reciting it was not the practice of the Messenger (blessings and peace of Allah be upon him) or of the Sahaabah.
As’ilah hawla Ramadaan
http://audio.islamweb.net/audio/index.php?page=FullContent&audioid=175728
See also the answer to question no. 69915.
And Allah knows best.