Why would a car respond late for speed when is accelerated?

Why would a car respond late for speed when is accelerated?
Although it can be related to ignition timing, most probable cause is fuel related; Such as, dirty or partly clogged fuel injectors, filters and lines. Also can be fuel pump not exerting enough pressure and fuel pump relay, which provides initial fuel pressure. Have air intake sensor checked, MAF sensors...anything to do with fuel air ratio. Best advice is to buy an OBDII unit, although expensive, it's worth its way in gold in the long run. that's all fine good answer but you might want to check your air filter first i had one with a ant nest in it.