Does it happen with O/D on or off???
I'm asking, because the first thing I do to get my car faster is turn off O/D... I only use it after I reach 60 mph., and turn it off when I want to stop quickly, or pass some dumb at the freeway...
anyway, you must wait 1 second to get response.
I also think, that it would be a good idea to get a Trans.fluid flush, and check sparkplugs.