I don't think there is a right answer for this as there's too many things that can or have been changed or are different between car(s).
Even if a car has the same aero, numerically, it might be affected because the min and max settings for aero have changed. For example, if there was a car with front aero vales from 50-150, and you had the aero value at 100, this would be half (50%) of your available adjustment.
But, if update V1.71 has changed the min / max values to 50-200, your '100' is no longer half of what is available, that would now be '125'.
This would affect your setup and how the car feels, except PD has really gone to town with screwing with people's setups as they have changed spring and damper values / ranges too. These are some of the values / variables that can be related to aero and subsequently how a car feels.
So even if you do return your car to the same aero levels of pre V1.71, unfortunately, there's no guarantee this will 'fix' the / any issue. The impact of this is also going to very according to what type of setup you had on the car, setups that had stiff springs will probably be less affected as these changes cater more for that type of setup, so you're less likely to feel a big difference.
This is made even more complicated as the aero changes across all car(s) affected are not the same, either numerically or statistically i.e. %. Aero updates are not +50 or -50 and neither + or - 50%.
That's just the setup, PP points / calculation also looks like it might be different, especially the WTC800 'grind builds' where having min / max aero setup was good for the PP rating.
Keep your eye on tuning section, I'll be posting something later.
In the meantime, I'm still going with this
Don't panic, save your old setup and try and be patient 👍
EDIT: without knowing what car and spec you're talking about it's hard to be specific with a right answer to or for the situation, if you post details or even screenshot of settings then that would make it easier to be a bit more specific