How old is the car and how much readings have you run? Did the rpm revs high as you press on the accelerator pedal but the speed didn't increase significantly corresponding to how hard the gas pedal is pressed, then your car is under worn discs. Also, slow pick up is likely to be caused by worn clutch discs. Check for thin, worn out, clutch discs.
Search Hyundai i20 Questions
Hyundai i20 Experts