Firm feel steering improvement?

I agree with checking the steering coupler. Also, not sure what you mean by "slop," but a recirculating ball steering setup isn't gonna feel like rack and pinion no matter what you do. But it should track in a straight line on a level road without your hand even on the wheel. If it wanders and needs constant correction, I'd be thinking your alignment is off.
I know this won't get it perfectly tight, I'm just asking if someone has benefitted from using these Firm Feel parts? I'm not trying fix it I'm trying to improve it:)