Hill power

I have a 1990 corolla 1.6 Gls. It comes with a 4af engine. I want some advice with gaining torque and power on it. This past saturday i was doing 171 Kph approaching a hill in fourth as i hit the slope the speed dropped to 130 kph. Is this right for this engine. What exhaust system do you recommend to make it sound nice and give her power.