NashT

At the very least pop off the hub dust caps and grab a torque wrench and hit the hub nut, S13 specs 108-150 lbs

If the vibration has been present with all those different wheels its most likely not a tire or rim issue.

And just food for thought, warped rotors can cause a vibration at all times and be worse at higher speeds, and if they are really bad when you brake it will vibrate/ shake the steering wheel badly.

But seeing that your saying its an intermittent vibration im thinking its more of a suspension component thats loose and when your hitting uneven ground thats when you feel the vibration.

I dunno bro, its hard to diag without looking at it in person. But theres really not that much to look at honestly. Do a shake down, left to right on the wheel will check tie rod play, pulling towards yourself from the top and pushing the bottom will tell you if there is wheel bearing play, and using a large pry bar under the tire will tell you if there is ball joint play.

When you did the solid rack joint and rack bushings did you unbolt the shaft collar from the rack? If so did you tighten it back?

When you did the tension rod bushings, if they are stock, did you put in the steel collar for the bolt in the center?

Im just trying to think of things you may have overlooked.

Also and most importantly, did you have this vibration issue before you replaced any parts? If not, then one of the parts you replaced is most likely the cause. Good rule of thumb is going back to the last job done if theres a problem