As the title says, I have a y8 with RC 550s in it, I used the y8 o-rings but they don't fit right and it leaks fuel. If I get d16z6 o-rings will the be the proper diameter for the intake manifold and the injectors to seat properly?

 

Get the thinner bottom RC o-rings and you'll be golden.

 

find one that fits the diameter of the hole on the IM and bore it out to fit the rc's

 

Will the Z6 o-rings work since they are OBD1 and so are the injectors...

 

If you already have the other z6 o-rings, then yes you can "make" them work. If your going to buy a new set, just buy the RC ones since they are designed to sit on thier injectors better.