+1 on R31nismoid comment...
i had stock engine and changed mine to -9's....i WAS not impressed with my 286kW, but now, after sitting in a gtr with -5's on stock motor, i am proud to say that i made a good choice of getting -9's!!!!!it is so much responsive....
and also thanks to R31nismoid for all the info that you gave me...
I personally think, it is better to start from the begining rather than taking shortcuts to do any mods....take stage's of mod at a time and you will notice the difference....
now i am going to see the difference of stock GTR compare to mine and i will see the difference....
Down side is i just got EPA for exhaust been too loud and i noticed that its gone louder compare to the sound i had when i had stock exhaust....better turbo's i guess...