Vague could also be, perhaps even more likely, control arms. Forgive my ignorance but does it have electric or hydraulic power steering? With the engine on and wheels pointing straight how much/far can you move the steering wheel before the wheels move? If it's much more than the typical steering slack (let's say 5 degrees??? total) then the tierods could be the culprit. If you have two people then repeat the test with somebody eyeballing the tierods, do they move obviously before the wheel(s) move? If so, replace. edit: You need to look at both the push and the pull motions on each side.
Wheels must be on the ground and suspension loaded for those basic tests to tell you anything.