Performer RPMs are dual plane, high rise intakes with 180 Degree firing order to produce incredible top end Horsepower while retaining good throttle response. Their larger plenums and runners match the free flowing exhaust, high lift cams and other modifications of a high output engine. They are intended for high performance street or competition engines that run up to 6500 RPM. They are not for emissions equipped engines. Edelbrock's performer RPM gives you the ultimate in street high performance