If you just modify sensibly you should be fine.. Ie no wheels that stick out of the guards, loud bovs etc.
You can always get things engineered but its usually an expensive process. With my previous 32 GTR, it had bigger turbos (factory position), pods (secured), bovs (hidden, not loud) a half cage, coilovers, camber arms etc.
I got pulled over by the cops and all they were interested in was my permit for my cage, everything else they didn't care about.
FWIW, car also passed pits with all those mods with the permit for the cage. That said, I know of people who have failed for camber arms and coilovers so its just your luck really. Cops "shouldn't" sticker you for suspension unless you're stupid low.
ECU was in the glovebox so I don't think they ever saw it. With a bov, make sure its plumed back and not atmospheric, pods to be secured. Upgraded turbos are iffy and best if in factory position not high-mounted unless engineered.