canny title to make you read

(no offence the yb is cool)
anyway what i mean is i hear lots of you (yb's)running 22,23,24-27psi of boost and only making between 300-350bhp maybe?
thing is i made 336bhp with only 17-18psi which is great. however i wanted more power
my mapper says he can't fit anymore boost in,as it starts detting.
he says i need to lower the C/R before he can do anymore!
so by lowering the C/R and then returning to the same boost will i have less horse power than before?
effectively needing more boost to make the numbers?