How do you tell if your struts are going bad? Should I just replace them now that I have 166k on the car?

If the rear struts are air then you will probably only have to change the front ones. If the rear ones are bad as well you will have to decide what type of suspension you want air ride or passive strut (like the front struts).

Go with KYB if you can.

Ty

Do the bounce test!

Bounce each corner of the car, get it going, and then let go. The car should return to the normal position in one bounce. If it keeps bouncing, then they are bad.