Cape Town - Brendon Hartley could have an advantage over his team-mate Pierre Gasly in Mexico this weekend with the New Zealander set to run the team's only upgraded package.
This weekend, looking to add to the four points he has scored so far in the championship, Hartley will have a new front wing and floor fitted to his STR13.
His team-mate Gasly ran the updates during the practice sessions at the United States GP, however, the rain meant the team wasn't able to evaluate the new parts and therefore reverted to the older specifications ahead of qualifying.
Hartley will use the updates in practice before a decision is made on whether to continue using them for qualifying and the race.
"Definitely there's a lot for the engineers to look at, data-wise," he said.
"I think Pierre wasn't happy with the balance in FP3 when he ran the aero so that's partly why they removed it.
"So it's going to be interesting to see how it performs, if we can get any more performance out of it.
"In terms of the rest of the weekend I think there's not a clear plan yet, it really depends how tomorrow goes."
With three races remaining, Toro Rosso are eighth in the championship on 32 points, four ahead of Sauber.