15" of vacuum? Carb it. It's not too low, but the MAP sensor or which system you rely on is going to fatten it up. If you're lucky to be able to run a Mass Air Flow Sensor within the intake sytem It can be "tricked" into seeing the right flow. This job is for somebody that has some time to figure out. Run a carb and be patient to learn to tune the system. If you would, please fill us in on more of what you wanna do. Too many ways to do this.