The TTbar deformation is an irrelevant deformation of 2D field theories associated with nonlocal UV behaviour. Despite its apparent solvability, many aspects of the deformation remain mysterious. In this talk, I will present exact results for the TTbar deformation of 2D U(N) Yang-Mills theory. Carrying out the analysis at the level of each instanton sector, we can determine the nonperturbative contributions to the partition function and prove that the spectrum undergoes a truncation (a property only conjectured for other TTbar-deformed theories). We then derive the large-N limit by studying the relevant flow equation, uncovering a rich phase diagram where phase transitions are driven by instanton condensation.