If it is just a temp sensor then i dont see a problem with just cutting it off, but Im pretty damn sure that thats the lambda sensor and for gods sake DO NOT CUT IT OFF, that sensor reads the emissions coming from the engine and tells the ecu if the engines burning up to much/too little fuel etc, if you cut this off your engine really is going to run like a box of frogs as the ecu isnt going to have a clue whats happening inside the engine, i think a new sensor would cost about £60 here which is a fair amount to pay but it is quite important, especially as the sensor would make sure theres no unburnt fuel coming through the exhaust which would kill the cat, and itll make sure theres the right amount of air getting and fuel getting to the engine.