Not sure what type of HKS turbo you have, but what is it rated too?
Why are you only concerned about peak power? So what if you only made 30rwkw more at peak, were you spend 3% of the time while driving . LOOK AT YOUR MID-RANGE BUDDY , it is farkin awesome, compaired to your previous tune. At 4500rpm you make a wooping 60rwkw more!!! That is a PHAT increase .
How much boost are you running, on the final graph? If you have more than 18psi, you may have reached the limit of you current turbo, and to get more power requires an upgrade. But more power means more lag, do you really need it?
I am a little concerned with your a/f ratios b4 5500rpm, they seem too lean. My tune has been made to sit at about 11.7:1, from the moment it reaches 14psi@3200rpm til read line. Best to keep it a little rich on a std bottom end
Have you tried to drop your exhaust b4 the cat? This will show you if the exhaust system is a restriction. Do you have a full turbo-back 3" exhaust system?
Has you mechanic placed restricters in you boost line, to increase the boost?