No official driveline warranty with a cam unless you go with Walkinshaw's top of the range W547 (supercharger, cam, exhaust etc.). The way I personally look at it is, Harrop (or any reputable company) will warrant their work and flow on effects, and the stock driveline can handle up to the 400RWKW, a cam upgrade is well within the driveline's capabilities. Personally any official warranty is not worth much as they always have a "misuse" clause, stating if the car is pushed and something goes boom, you're not covered (not a direct quote ).