Hyundai Repair: loss of power on highway, car speed, performance issue

Question
when i reach the highway the car is loosing speed and i have to push pretty hard on accelerator to keep the car speed.
I got an Accent 1996, 1.5liter sohc.

Answer
This could be an engine performance issue, a transmission/clutch issue, or a brake issue.

Is your check engine lamp on or has it been coming on?  If so, check the diagnostic trouble codes stored in your engine and transmission control modules.

Is your engine rpm abnormally high when the problem occurs?  If so, suspect a problem with the transmission (automatic) or clutch (manual).