No you don't have to have one for that amount of boost but you will have to run better fuel for that boost then what you would if u had a head shim. ie 12lbs with shim 91 octane would be fine 12lbs without shim c-12 14 probroly have to go c-16 you'll have better responce without shim but can make more power with shim cuz you can run more boost