Long story short, my 96 4Runner SR5 4WD with almost 250K miles was starting to show it's age on the front end. Took it to a shop who said the rack and pinion was shot and I agreed and also noticed lower ball joints were bad on left side so I decided to replace both ball joints, sway bar bushings and stabilizer bushing. The upper ball joints had already been replaced a few years ago, about 5 so they were still good.
Now after all this work, the front was jerking to the left when I hit the brakes. Yesterday after taking it back to the shop for the 3rd time it now jerks to the right when I hit the brakes and it gets real squirrley.

Is this an alignment issue, as this is what the shop told me it was when I took it back yesterday to fix it from jerking left?

 

So you did replace the rack and pinion?
I'm having a bit of the same problem, but I did have mine aligned. Have you checked your inner and outer tie-rods? By 250K I bet they are worn out too. I don’t know if you have a lift on your truck but what I ran into after doing all tie-rods, ball joints and bushings is too much positive camber. Schwabs claims they cannot adjust the camber any further due to my spacer lift. That may be true but it was fine until all was replaced. With too much positive camber you may get jinks in either direction as you brake, accelerate, or change lanes.

Personally I would start with a look at your tie-rods followed by at least a check of your alignment. You can check yourself. This video is a bit basic and amateur but it helps:
Good luck!