Anyway, I think I have figured out how to unlock K&N. Every discipline has three tiers, and every tier has three championships: a short one, a medium one, and a long one. The game specifically tells you that if you meet the team objectives in the medium championship, you will attract the attention of the bigger teams. Winning unlocks Ravenwest, but if you just meet the objectives, then other teams become available, both in that championship and the longer one. For example, I did the Tier 1 medium championship in Open-Wheel with Razer and finished second, which unlocked Monster in all three championships for Tier 1. So to unlock K&N, I reckon that you have to fulfil all of your team objectives in a medium-length championship that K&N race in (usually Tier 2 and Tier 3; I have only ever seen them in Tier 1 Endurance races) without winning the drivers' title.