Wira 1.5 performance

[sicness80]

hi all,just like to know wira 1.5 sedan manual (injection) can modified/change/upgrade which part to be more powerfu?(standard modified),my car had done 4.2.1 extractor with center piping 2.0,mushroom air filter,flywheel 1.8(super touring) with clutch set.since now i can feel car performance increase abit,i dun wan to change turbo system or powerful engine,im not racer,i just wan my car performance can be more better than other standard car,so i think all sifu here can teach me something to increase performance again,port&polish?big thorttle body?re-programing ECU?power plug cable?performance plug?anyway i wan to learn all.thx very much.:X-: