Actually, not as much as you might expect. Tawantinsuyu reached across the whole of western South America, yet its most glaring geographical boundary is not the Pacific, but the Amazon Basin. Groups in the Amazon were known to an extent by Andeans and coastal dwellers, but it is a dialogue archaeologists are still sussing out. It is possible that Amazonian groups could get over the Andes through passes in what is now northern Peru, bringing ceramic technologies to the mountains and western coast as well as their own cosmological input. Sites like Chavín de Huántar popularized and spread an ideology that affected some five hundred miles of coastline - with distinctly Amazonian aspects in its icons and outlook.

We have evidence that many Andean civilizations skirted the Amazon - the Wari made one of their trade routes out of Ayacucho toward Cuzco along the eastern edge of the Andes at some 1000 m above sea level, along the lower yungas foothills. Likewise, the Inca named their northeastern quadrant Antisuyu, for their allies there the Antis. Undoubtedly elements of the Amazon made their way into Cuzco, the heart of the empire - tropical fruits and plants are accessible today, as then, in the daily markets of the Cuzco Valley. However the Amazon doesn't lend itself to conquest and control like open mountain peaks and passes passes do, or wide coastal deserts and river valleys. The severe altitude difference for Andeans like the Inca meant that pneumonia and sickness could decimate military movements into the jungle. So for the Inca, whose empire was one of the most direct and bureaucratically-driven polities ever to develop in South America, why throw an empire's resources on a space that could never be directly controlled? Many of its resources could be curried through clever agriculture in the yungas or political alliance/marriage with constituent groups of that region.

The Sacred Valley, which holds Machu Picchu, Ollantaytambo, Choquequirao, Pisac and many other royal estates of the Inca, was thus supported as a lush hinterland of the empire, even as it stood at a fringe of the empire. Machu Picchu and Ollantaytambo served both as verdant oases for the Inca and his retinue and as excellent defensible fortresses - a conscious projection of Inca dominion on its most consistently vexing frontier. In a way, the strongest presence of the Inca state in the east was after the Spanish arrived and took Cuzco from the Inca. Moving up through the Sacred Valley to the yungas beyond, the Inca established themselves at Vilcabamba, beyond the reach of Spain for some decades. Aided in this by groups like the Antis and Chunchos, the Inca state and its religion persisted until its complete discrediting and decapitation by the Spanish.

Now, I'm not really an expert on Amazonian groups, but I do understand that they were on some level were in contact with coastal and mountain groups in South America. Trade and associated ideas changed hands and minds for millennia - and yet even the Andes' strongest direct power could only work superficially with a whole swath of a continent. The dialogue between the coast, the mountains, and the forest is definitely one of the biggest questions out there for South American archaeology.