Im currently running 720cc primaries and 1680cc secondaries. I was thinking how much more fuel the 1680's flow compared to stock and how maybe the diffusers are possibly blocking fuel. I know what they're there for but they were only meant for 550's. Do you guys running 1600's pull them or keep them?

 

Unless you have a set of injectors with a very well designed spray pattern, it would be more important to keep them in with the larger injectors.

 

I keep mine. The spray pattern of the 1680 is still very similar to the stock injectors. It's a very old design.