Also own a 2005 Cerato LX Hatchback... I must say, i only have 4500km on the clock, but it's been a total pleasure driving those, and the car has lots of power, and fuel economy also not a problem... just a little better than the average 1600 motor, but I don't mind.
If you are having performance problems, perhaps have a look at the air filter. I have read in many places that this is a known problem with the standard Cerato, and that it doesn't work too great. I haven't experienced any problems yet, so I havn't looked at replacing it, but it is on my list... Perhaps a Cool Air Intake :grin:
Also, judging by the lack of replies, I would say your problem is pretty unique... Perhaps a factory fault of some sorts, but definitely, your performance is not an indicator of how the car usually performs.
Have not jet looked at the airfilter but as we are also at 2500m above sealevel it will have some sort of effect. I have spoken to the people at DASTEK to fit a pigiback chip to the car but I first want to take it up with the dealer as the car was also sold with a service plan,so I am in a bit of a dilema.
As it is my wife's car and she has to drive about 80 Km to work and back and with the current fuel price (R6-00 = 1$per litre) it becomes fairly costly.