I have a 1999 blazer with a 4.3 I bought the upgraded GM injectors and the felpro intake gasket set, i also bought from GM the seal injector kit part # 17113205 do any of the black o- rings get used or were they put in the kit for use if you were going to rebuild your injectors???

 

The kit is universal for both v8 and v6 use. There are o-rings for the fuel inlets as well as each individual connection into the main injector body.

I do not believe that you need this kit when you have the MFI spider. If I remember correctly from when I had done the MFI swap and LIM (both at the same time), the MFI kit came with all appropriate o-rings.

 

So I need to put an o-ring into each fuel injector inlet on the intake then push the new style injector into the inlet?? looks like there is no o-ring used in the intake inlet with the old style injectors?

 

NO. The larger o-rings that come in the kit are definitely not needed in your case. They would only be used if you removed the individual injectors from the main injector pack body (remove the plate from the bottom, then pull out each injector. I do not believe you need to even have that kit as I am fairly sure that the MFI spider comes with new o-rings/spacers.