Remember if your catalytic converter is dirty it will significantly decreases your car power.
Cleaning you catalytic converter will restore your car power to stock specification
Removing your catalytic converter if its dirty will also restore your car power but slightly below stock specification because now your car is running rich. (i. E there is imbalance bw air and fuel mixture)
In moderen cars like reborn down piping also requires tunning car on dynamo and i think Unchip Pakistan in Islamabad and some shop in lahore have them
If you downpipe yor civic and then unchip it thats how you can get maximum performance from your civic
