Orite fellas

doing a bit of reading and i wanted to know i wana run a turbo on my 325i sport m tech 2 know the compression is high at 8.5.1 or 9 something not sure the exact pressue i wana drop the compression and strap a turbo on to it running about 12psi

Will the pistons have to be chnaged im new to moded engines but am going to do the work myself