Mine was stock, never got to ask other driver.I had a race with a tuned ,headers,ported 2018 manifold,cai 2014 and had a fender on him from 40-100+.I personally would try to get an 18 up a10 car.
I had a nice 20-100+ roll race with a 2014 gt manual with lth with no cats, cai,and a ported 2018 manifold. My a10 is stock and I managed to keep a half car on him at the end and niether was gaining or losing ground at that point.