Those numbers are with the stock tune. Once an aftermarket tune is factored in the exhaust only gains rise to 20 horsepower. Not, the dyno used is a MAHA dyno and dynojet figures Americans are accustomed to will be different. The delta shows considerable gains and that is what one should focus on.
Take a look at the stock headers versus the Supersprint headers:
Torque will be picked up by ditching the cats hanging right off the stock cast iron manifold. The Supersprint long tube headers are a much better design.
Front pipes with a hi-flow cat are also available although ditching these cats for a race pipe will offer greater gains but this is the responsible setup:
Here is the mid-pipe with resonator:
And of course the rear section muffler:
The entire system is modular so buy it all at once or a piece at a time, up to you.
MAHA dyno graphs.
Baseline, pump gas:
Pump gas, exhaust only:
Comparison between ECU tuned car with stock exhaust and Supersprint exhaust: