While you wait for an answer about the ancient times, I can perhaps give a sense of its culture and position by the civil war after the Han's collapse.

I would recommend getting hold of a copy of J.Michael Farmer's The Talent of Shu: Qiao Zhou and the Intellectual World of Early Medieval Sichuan whose main subject is the Shu soothsayer and historian but does go into the culture of the area, particularly the scholar attitudes from within Yi and towards it in chapter 1 but also in other chapters.

The area was a good place to launch one's ambitions for empire as Liu Yan did and it became Liu Bei's home for empire. The valleys were fertile with long growing season and rich with natural resources that led to the nickname Heaven's Storehouse from the third century onwards, there was trade potential through Jiao and through the Nan tribes into places like Burma and Tibet, it's mountain passes and riverways meant it could be hard to take from the outside and its roads could be cut off from rest of China during times of chaos. With distance and terrain, the people of Yi would not always align with the rest of China and Ban Gu would suggest their prosperity led to the locals being easy-going, profligate, weak and mean.

Former Han official Wen Weng, portrayed by Ban Gu as educating the region, built a popular academy and, using the purchase of the region's famed brocade and book knives, to fund sending some low level-officials to the imperial academy at Chang'an though Ban Gu still questioned the moral character of the locals and disdained their willingness to ridicule in their writings.

The area developed a distinct scholarly tradition that did not always help them at the Imperial Court. As well as Ban Gu's complaints, they liked rhapsodies that wouldn't gain approval in Central Plains as a major strand scholarship during the Han times (even during the dying days of the Han, Cai Yong bitterly opposed a school set up by Emperor Ling for such scholarship). Over time as the Former Han drew to its end, the scholarship would remain broad-based but there was leaning towards reading the Heavens, of divination and the like, of embracing Daoist texts and the esoteric.

When the Latter Han court used such men, it would be for their skill in prophecy and for that, they could be valued highly depending on the inclination of the Emperor but Yi scholars were not made Ministers or Excellencies. Yi scholars did not always embrace the chance of serving at court or in the provincial ranks and would turn to teaching (also less risky). The local gentry took pride in their lands and their history, tracing a scholarly lineage from masters to students who then taught their students and several writing local biographies.

In the three kingdoms, as examples of local pride, Qiao Zhou's four works on providing a local history of Yi based around its geography and produce to link Yi to the centre of power and history. Qin Mi responding most strongly to doubts from visitors about the quality of the men of the region while claiming Sage Kings of old had been based in Yi. Or in Chen Shou's pride in his Yi education and contrasting his local mentors and noteworthies with the quality (in scholarship and personality) of the Jing and Central Plain rivals in the kingdom of Shu-Han or creating a separate work of biographies of the scholars in Yi. Later historian Chang Qu's writings about the history of Yi argued it had a long tradition of scholarship