Which AEM water/methanol controller should I choose (35 psi or 40 psi max)?

AEM controllers differ by the MAP sensor range. The standard controller with internal MAP (30-3304) is rated to 35 psi boost, the HD controller (30-3306) to 40 psi. Choose the one that covers your maximum boost with the best resolution; for lower boost the 35 psi version gives finer control.