Question on steering gear box

I replaced the steering gear box on my 87 towncar, because it had too much play and leaked.
The new one (an after market one, not a Ford part), is going fine except I
find it is very sensitive...
Question : Is there any way to make the steering a bit stiffer? what about that set screw on top of the gear box, what is it for?
BTW, The car had an alignment after the replacement.
Thanks in advance!
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