Depends on your air charge temp. I get 26 psi out of stock turbo and my 49 is set at 25 psi now. There is no particular sweat spot for ones car because of the diffenent combo's. I run alky and it cools the charge like its a 50 degree day out in 80 degree weather. FM, I have no experience at , but im sure it cools the air charge very well also. If you run race gas on a stock set up then I would say around 24psi
HTH
Bo