EFI

I have the Holley dominator 4500, which is probably the most expensive of the Holley units, but everything I needed was in the kit. As I recall it even came with the O2 sensor.
The 4150 style units are probably cheaper, but Holley is expensive.
In their defense, my unit was starting to have issues with the secondaries not closing fully. They replaced both throttle shafts and butterflies and tested it for holding vacuum and closing properly. The unit was 3 years old, but they fixed it for free and sent it back to me on their dime.