stage 4 (not running right) vs 2010 GT

so me and my best friend had just finished eating at a hot dog joint
he was driving his mom's 2010 GT mustang auto (since he just had knee surgery and couldnt drive a manual)
he felt pretty confident that the GT would not have any problems against my car
we did a few pulls, most of which were from about 35mph
each time i waited for his car to kick and start pulling before i hit it
and every time we made a pull i would pull away on him pretty well (mind you that either my tune needs to be redone or my fuel pump is going bad)

i didnt expect to beat a GT and to my surprise i did on a not so good running stage 4