The document presents a theoretical political-economic model that analyzes how corruption and foreign direct investment (FDI) interact to determine an optimal institutional policy level in a developing country. There are two types of people - honest people who work in the private sector, and dishonest people who work for the corrupt civil service. The model considers the costs to firms of paying taxes through both legal and illegal structures, and how the institutional policy level affects these costs. The optimal policy level depends on the relative efficiency of the legal versus illegal structures, as well as the degree of corruption in the political process and the size of political contributions from dishonest lobby groups.