Holley EFI Dual-Sync Distributor Chev 350 454 # HO565-200BKHolley EFI Dual Sync Distributor Chev 350 454 # HO565 200BK Introducing the next generation of Holley EFI Dual Sync Distributors, the new design features an improved shutter wheel, high quality dual Hall Effect sensors, and an MSD cap and rotor! While these distributors are designed to be used primarily in sequentially injected installations, you can easily use them as a crank trigger for TBI system also. The precision machined shutter wheel design