Exactly!! If you want to turn the boost up, then you have to ask your dealer about fuel mapping. If the map will work at 15lbs then no problem. But like glengine said, the guage is less money than the engine. I think Nick from Vernon Motor sports was running more boost on his MCX Phazer. I am sure Swenson was as well. Maybe you could start there.I look at it in the manner that an A/F gauge is alot cheaper than a motor and turbo rebuild.. But if you stick to what it was tuned for then you shouldn't need one.