I’d pick China as my civilization of choice, given its size, resources, and relative political stability. After finagling my way into the high ranks, I’d try to instill a culture promoting scientific advancement, start educating the peasantry, establish scientific academies, and so on.
I’d probably introduce the concept of internal combustion too, since that’s about the right technological level for them to grasp and apply widely. I’d bring all the science texts I can back, and start transcribing them, hoping that it will eventually make sense and be applicable. 2,000 years later, though, the social change of promoting scientific progress will probably be more significant than any knowledge I could bring back.