ECU & Harness MPFI Kit

The ECU & Harness MPFI Kit from HOLLEY (SKU HLY550-604) is a complete engine control solution designed for builders and enthusiasts upgrading to multi-point fuel injection on carbureted or throttle-body-injected platforms. This kit addresses a critical need in the EFI conversion market: eliminating the guesswork of sourcing compatible ECU hardware, wiring harnesses, and sensors individually. Whether you're resurrecting a classic muscle car, modernizing a street rod, or fine-tuning a performance swap, this integrated package streamlines installation and ensures proper communication between fuel injectors, ignition timing, and engine sensors.

At its core, the MPFI kit includes a pre-programmed ECU and factory-matched wiring harness engineered to manage multi-point fuel injection sequencing and spark advance across varying load and RPM conditions. The harness is designed to minimize installation errors by color-coding critical circuits and incorporating OEM-style connectors that eliminate the need for custom splicing or terminal-by-terminal fabrication. With a compact footprint and manageable weight, the kit integrates cleanly into most engine bays without requiring extensive modifications to support structure or wiring routing.

HOLLEY's proven tuning software compatibility means you retain full diagnostic and adjustment capability post-installation. This kit is ideal for restorers and hot rodders transitioning from carburetors to fuel injection, providing a reliable and efficient solution for modernizing engine performance.