Joined: Nov 2016
The PS idler arm is 'springier' in design, but it still uses rubber to help return things to center a little. IMHO, you are better off with the manual idler arm anyway, and for better RTC, use better alignment specs with a little bit more caster. Less resistance when you are sitting in a parking lot trying to turn your modern radial tires (which hang onto the pavement a whole lot better than the old bias ply tires ever did). That puts less strain on your power steering equipment. However, since you already *have* the PS idler arm, I sure would not bother spending money to replace it, if it's in good shape. If your elastomer is all cracked and shot, then yes. Replace it, and you might as well get the "manual" version.
When you're driving, using 5+ degrees of caster will improve your car's high-speed stability, add camber to cornering (letting tires stay flatter to the pavement and increasing grip), and improve return-to-center significantly. Even a non-PS car needs a lot more caster than the original specs call for.
Just make sure the idler arm and pitman arm are basically the same length (I know they're not straight) so that the drag link winds up parallel. If it's cocked at an angle, you'd have problems. Otherwise it should be fine.
I would be surprised if their custom pitman arm is an odd length, since they don't insist on you using their own custom idler arm, so this is probably a complete non-issue.
I smile a lot. It makes people wonder what I'm up to...