I think we're getting a little mixed up here There is the MAP (manifold absolute pressure) sensor and the amal valve. The MAP sensor detects the level of boost and the amal valve acts as a electronic bleed off valve. It has been said that the amal valve is weak but I known them to give no problems on levels of 30psi boost. If the amal valve fails it usually fails closed and you get less than maximum boost. The true reason why some tuners take them off is that they don't know how do alter the ecu code to allow for the extra boost (sloppy in my opinion when you pay good money to upgrade your car). Another downside of removing the amal valve is that it's also used to protect the engine e.g. not allowing full boost until up to temperature or in case of sensor failure.