Abstract: A device for automatically adjusting fluid flow into an engine intake includes a body member adapted to mount upstream of the engine intake and having a fluid passage therethrough and an aperture therein intersecting the fluid passage, a plate slidably insertable into the aperture and having a bore therethrough corresponding to and registerable with the fluid passage when the plate is inserted in the body member, and a variable orifice operatively disposed in the bore and thereby defining an opening area which is automatically variable and dependent on fluid throw through the orifice demanded by the engine at a given RPM. This device can be used to handicap one racer or to establish engine performance parity in racing vehicles by mounting the device between the carburetor and engine intake of each vehicle.