power_up

Recently, I notice that when I drive my car, power delivery seems not very linear compared with my friend's 964 which is like new condition. When I drive my friend's 964 (targa tiptronic), press little throttle is already feel instant response. It feel light in weight. Compare to mine, also a tiptronic gearbox, look like driving a heavy car, I need press throttle deeper to obtain power, especially from stand still. It look like I need to wait for power coming. Power after 4000rpm of mine is strong though.
Any idea what mine going wrong? What parts are being aged and will as a result of that?
Thanks.

My 964 is 1991 tiptronic. 20000km after engine rebuilt done by previous owner.