Ok, the "book" you are reffering to is the issue of HPI when they talk about doing an 11 second pass on a RB25 Skyline and how to achieve it.
First thing's first, if you are running the stock turbo with a great tune, good amount of boost and everything else is up to scratch you will be running around 200rwkw if your lucky.
Depending on your mods (ie if your car doesnt have a tune you have no hope) you could be anywhere from 170-200rwkw. So your figure of 250rwkw is WAY out.
Second that HPI issue was a bit missleading (probably possible, but very few cars perfectly setup can do such a thing, way to many variables), most stock turbo
skylines with a tune and good setup crack into 13 second passes. Yours would most likely would be in the 14's, so once again, way off 11 seconds champ.
Not trying to hang shit on you mate, just trying to educate you a bit so you don't go around saying stupid things.