if u have your subaru dealership install your after-market upgrades
does it still void the warranty?

or no?

You would have to ask your dealer. If they do the install, there should be a warranty on the work performed (the install of the parts, not the parts themselves unless they are SPT parts), but they could still technically void the warranty on your car.

read up on it, they can't legally void the warranty - they can deny the repair if they can prove it was mod related, on per-case basis

If they sell it, they installed it, they will NOT void your warranty. However, it doesn't hurt to ask and always keep your invoice. There's a Toyota dealership here that does TRD install and it doesn't void your factory warranty @ all, plus they add a 1-year warranty on any TRD part they install.