Exhaust Manifold Absolute Backpressure kit will allow you to log back pressure to your ecu or datalogger.
primarily used in Turbocharged applications.
To keep it short and sweet; If you turn your boost up and you're over a 1:1 ratio of boost vs. MAP you are likely out of turbo efficiency.
Kit includes.
EMAP canister
3 ft - 1/4 .035 copper tube
1 x straight and 90* 1/8 to 1/4 compression fittings
1 - AEM 5-bar map sensor.