New ones from Merlin are $110 plus o-rings, aftermarket (no one has listed but they do for the same engine in a Trooper/Rodeo) are $79 special order here in TX. Misfires can also be caused by low octane fue, lean conditions caused by vacuum leaks, or carbon build up on the head/valves that causes the engine to need higher octane fuel to avoid misfire/pinging.