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There Are Lots Of Places Selling EFI Conversion Harnesses, But There Is Only One PSI

PSI Harnesses

What separates a PSI harness from everyone else?

A PSI harness is tailored to Your engine. We produce over 100 different engine harnesses. What does that mean for you? It means that you don't change your engine combination to match our harness, we build the harness around your engine combination.

A PSI harness is made in America. PSI harnesses are proudly made in the USA, just like your classic car was. That means we have total control over the quality of the harness. That also means that you can feel proud knowing that men and women in the USA are employed to produce your harness.

A PSI harness is made with top quality materials, to standards as good or better than OEM. A PSI harness can withstand that heat, cold, vibrations, oil and gas present under your vehicles hood. PSI harnesses are constructed from from Brand New GM Delphi Connectors and TXL (Polyethylene Cross Linked) High Temperature Wire to GM Specifications. All splices in the harness are "sonic welded" so you dont have to worry about a splice coming apart. Don't trust a harness from an unknown source or made with unknown materials, it might save you a few hundred dollars today, but it will cost you down the road.

PSI also has the capability to produce customized harnesses in small volumes. If you have a need for a harness for a specific application not offered, feel free to contact us. For additional information you can email us at

Customer Service

PSI Has a well deserved reputation for outstanding customer service. Our customer service department can be reached by phone five days a week, and by email 24 hours a day. You will reach someone knowledgeable in EFI conversions and willing to do what it takes to get you on the road.

Our tech support specialists have decades of General Motors experience. On a daily basis they go above and beyond to get your swap on the road (or sea or air). We have diagnosed tuning issues on high end custom cars just before they cross the auction block, gotten gauges functioning on airboats in the everglades, or provided installation trouble shooting on a drift car right before a competition.


With a combined 25+ years experience, the owners of PSI were looking for a foolproof solution for electronic fuel injection conversions into older vehicles. With no appreciable support from the automotive aftermarket, PSI was formed. We continue to develop components and kits to meet your needs. If you don’t see it on the site, feel free to contact us.

Fast Shipping

In a rush to get your project on the road before a big car show, cruise or special event? Don't wait 4 or 5 weeks for your harness to ship. PSI LS swap harnesses are usually in stock and usually ship within 1-3 business days. Since COVID shipping times have been delayed; please inquire for lead times as some harnesses may vary.