Simple question, have searched. At what point is a new fuel rail needed? What is the maximum size injectors that the FD can accept without a new fuel rail? I have been told that going to 4x 850 is about it....
Thanks for the Help
Adam

 

Without changing rails, you can do 850's in the primary rail as you already mentioned, and 1300 can fit into the stock secondary rail (as they are just bored out 850's).

Common setups are 4x850's or 2x550's & 2x1300's.