I'm going to replace my manifold when I am doing the stage 2, get rid of the plastic one. I'll probably use the S&S version. Is it necessary to replace the orings on the injectors and sensor? I've watched videos on YouTube and no one replaced those orings.

 

No it's not but why wouldn't you? They're cheap enough, and if you tear 1 you'll have to stop and runout to get one.
Holding up your progress. And if you're ordering parts, you'll have to wait for delivery.

 

Harley only sells them in a kit with screws, somewhere around 30.00, or more. Its part number is 91800058. They don't provide a part number for the orings individually. Can someone help me out with the part numbers needed for just the orings, its for a 2020 Milwaukee 8. Is the sensor and injectors the same oring?

 

One thing to note is that most of the injector / throttle body O rings might be metric.. I know for sure that the cable driven TC throttle bodies were..

 

McMaster Carr is one source for O-rings.

 

I replaced mine on a '22 Low Rider a couple months ago. Did not replace the O-Rings. Shame on H-D for that plastic manifold. Mine had a crack that caused a high idle when coasting. It was the devil to figure out.

 

https://www.cometic.com/products/C10200