Depends how far you push them and whose tune it is tbh, Golf 8R is basically a 5 cyl with one missing, they will do around 100hp per cylinder on std rods, so an RS3 will do around 500 hp, but perhaps the mid range torque needs limiting.
Big problem with 5cyl is the cylinder pulses and the length on exhaust tract from cylinder 3 to turbocharger, early RS3 had EGT monitoring (Exhaust Gas Temperature) which protected the engine, my lads RS3 engined Golf Mk2 is limited by EGT as to how hard you can push the tune, it will easily see over 1000c, the Syvecs ecu is programmed to put lots more fuel in around the 975c to try and cool it down.
A lot of tuners found the EGT getting in the way so disabled it ***...................ends up with either a knackered piston or the piston starts to seize and causes the rod to break, always piston number 3
When I rebuilt/forged his RS3 I thought I would try and sell the old pistons on ebay, I sold all 5 individually over about 4 months to presumably people who tried too hard with the tune