We have a Sierra 2.0 CLX DOHC built in 1991. Yesterday I noticed, when I wanted to start in the 3rd gear right up to 100 km/h, that it only pulls well, if you push the accelerator pedal about half through, but then you push the accelerator further through, no more extra power. What can this be about? Is there something wrong? I know that we will soon get a new air filter and an oil change/new oil filter. Does that have something to do with it, or is the engine because of the age of 12 years just not so powerful? But I think the problem was already there when the air filter and the oil were new. Maybe there is something wrong with the pedal?? I’m sorry if the stupid questions are, but I don’t really know about car technology.