Some general conclusions out of Buzurg's book
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In this book: The Wonders of India, 45 of the about 130 stories are connected to India or Ceylon (Serendib), China: 14, Zabay + Lamira (Indonesia):11, Waqwaq:7, The gold bearing country: 7 , Zindjs:12, Ethiopia (Habashi):1 (Many others are connected to Arab places)
We can conclude that travel to East Africa must have been frequent out of Siraf were Buzurg collected these tales.
The geographical places in Africa that are mentioned are: Zindjs:3, Sofala of the Zindjs:4, Sofala:1, Land of the Zindjs:4, Highlands of Zindjs:1, Sea of Zindjs:1, Kabila/Qanbalu/Qabila:3, Thabia:1, Island of Ghileni:1, Sea of Safou:1, Sea of Berita (Berbera):1, Berita:1, Zeila:1, Abyssinia:1. Sea of Habash:1, Cairo:1, Nile:1, Assouan:1.
We can conclude that the lands of Zindj and Sofala are the only places in East Africa that were often reached from Siraf.
When reading the book one notices that  the gold trade of Sofala doesn't get mentioned. Most probably because no specialized gold trading centers had come into existence yet, (Kilwa and Sofala town). The gold bearing countries are often mentioned, but they are Malaysia and the interior of India. The gold digging in the country of  Zindjs is mentioned but includes mythical creatures, pointing to the fact that no first hand knowledge is available.   

In every edition that I consulted the numbers for the tales were different, because they let out here and there a story. My numbers as a result are a kind of compromise between the different editions. 
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Note on tale 36
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Gold mining in the Zimbabwe area started from the ninth century, (according to archeological evidence.) So there the story might be correct.

Where the gold digging ants, big as cats are mentioned, we have to do with a much older tradition, started in the Hindu epic "Mahabharata"(Sanskrit) from 1000 BC. The ants are first mentioned in the west by Herodotus (430 BC) after him Neachus (4th century BC ) and Megasthenes (3th century BC) Then Nearchus, Agatharchides, Strabo. In the second century AD Philostratos and Solinus put the ants in Ethiopia as well as India.
The 6th century Christian Topography also includes an ant. By now it has grown into an ant-lion.

Note on tale 117:
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On top: Sculptures of outrigger boats capable of crossing the ocean are found at Borobodur
Under: Outrigger canoe as the Malaysian people used in the days that intercontinental travel was over.
Taken from : India Orientalis.-Part IV. [by] Bry, Johann Theodor de , et al. 1600 (based on then about 30 year old travel accounts).

Visitors to East Africa

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Name: Abu Muhammad al-Hasan ibn Amr ibn Hammawayh ibn Haram ibn Hammawayhal-Najirami.

Origin: Najiram, north of Siraf on the Gulf Coast.

Profession: Possibly a merchant or traveller.

Sailors tale: 33 Gave information about the birds on Qamar.

Name: Abu Abdallah Muhammad ibn Babishad ibn Haram ibn Hammawayh al Sirafi.

Origin: Siraf

Profession: One of the principal shipmasters to sail to the Land of Gold.

Sailors tale: 74 Talks about giraffes in Lamery (Indonesia).

Name: Isma’il ibn Ibrahim ibn Mirdas (Isma’ilawayh)

Orign: unknown; possibly a resident of Oman.

Profession: One of the best shipowners to go to the Land of Gold.

Other: Son in law of Ashkanin.

Sailors tale: 9, 31, 32, 33, 36, Talks about the wale in the sea of Zanj; About the slave ship going between Oman and Quanbalu. About soothsayers in the land of the Zanj. About giant ants in the Zanj interior. And about giant feathers found in the land of Zanj.

Name: Abu al Abbas

Origin: Siraf

Profession: A chief merchant in an Indian town.

Sailors tale: also 33 About giant feathers.

Name: Yazid

Origin: Oman

Profession: A ship’s captain who used to go to the Zanj country.

Sailors tale: 92 About the result of the big bush fires.

Name: Ja’far ibn Rashid, known as Ibn Lakis

Origin: unknown

Profession: A sea captain who was well known on the Land of Gold route and a shipowner.

Sailors tale: 117, 118, 119 About the Waqwaq people (from Malay-Indonesia) hunting slaves in the islands of the Zanj (Kanbalu). About a ship heading for Kanbalu but driven to the cannibals. About him being in Sofala of the Zanj and meeting a giant bird.