%META:TOPICINFO{author="sonictronic" date="1140680119" format="1.0" version="1.1"}% %META:TOPICPARENT{name="ECUHardwareMods"}% A dual runner manifold like on the F22/B18C1/H22A has two passages for air to flow. When in a low rpm range the long runners are engaged to promote torque production. When the engine reaches a higher rpm the butterflys open and let the air go through the short runners which helps with high rpm power.