Temp3st, what other mods do you have on your car? Can you list everything that has been changed? If it's stock and you have flatspots - go to the mechanic.

If you have lots of mods and no tune, this can be the reason. Even something that appears small like an intake can give you flat spots. If you have an aftermarket intake, try fitting the stock on back on and then see if the flat spots are gone.