Next logical bolt-on...
 

I'm looking for suggestions on the next tuning step for my Z.

I got Stillen Gen3s, Berk HFC, and should be receiving my F.I CBE soon.

Not considering pulleys or long tube headers (I'm planning for FI at some point), what should be the next bolt-on?

Is it the M370 manifold?

Tuning will be done after all bolt-ons are in place.

If you plan on going FI I wouldn't get the M370 as it supposedly has thinner walls that cannot withstand boost.

I would recommend going with a lightweight flywheel and better clutch. This way it will give you a better drive stock, but can also hold FI power.

Only other options are better suspension and tires.