so then a fcd is pretty safe with a rb turbo back and an upgraded fuel pump?

keep your eye on the boost gauge if the boost gets to high let off the gas. just be careful. my car has a panspeed tuned ecu for 11psi the S5 have a solenoid to control it. my car didn't creep much occasionally i saw 13-14 psi on the highway but no signs of detonation even with stock fuel pump

You should be ok as long as you don't go past about 10 PSI. If you get a fuel computer then 10 PSI will be safer with the stock IC. If you get a good intercooler then 12-13 PSI should be ok.