Only in a cramped dyno cell will an intercooler show a weakness. On the open road with tons more airflow and plenty of heatsoak recovery time, it'll be fine.
The measured power is only for that particular set of conditions - I.e. a little room with only a fan for airflow. Out on the road, things are very different. More airflow and lower ambient temps.
Don't blindly follow the herd and bolt things on for the sake of it. Get confirmation the S3 cooler is restrictive from proper testing first. Stage 2+ turbo speeds kind of super heat the intercoolers anyway. You'd be better off running a bigger turbo to make the same power from more cfm and less pressure, and therefore less heat.
Good luck for Friday
I'd be happy with anything over 350hp on these old engines and turbos