primera p11.144 tuning

Hello all. I'm new user form Poland. i'm writing here because I looking for my Power Horses lost during tuning ;) I was expecting about 170 HP and It's only 152. Here's the car: Model: Primera P11.144 Engine SR20DE Year: 2000 Exhaust: SSAC 4-2-1 header + custom 2,5" exhaust Other tuning...