Car pulls suddenly at high speed
 

My mechanic and I can't figure this one out. I have a 1999 S70 with 162k miles on it and after a 250 mile roadtrip on smooth roads, i.e. no pot holes, it started to pull intermittently hard to only the right side. Sometimes it pulls hard, other times it doesn't. If it is pulling hard and I stop for 5 minutes it goes away for a little while. Sometimes it acts up right away, other times after it has been on the road for 30 to 40 miles. I needed a brake job before it started so I replaced the rotors with Brembo, purchased (2) rebuilt front calipers, and PBR Metal Master pads, and the problem persists.

Does anyone have any advice or have experienced this in the past? When it pulls it is not a constant pull, the wheel is jerked to the right. If it has been acting up and I pull into a parking lot and let go of the wheel when I am driving less than 5 mph it will pull to the right by jerking the wheel in 3" movements. Any advice on how to correct the problem??? Any advice would be greatly appreciated... I drive 30 miles to work everyday and have already had a close call with a fellow commuter due to unexpected jerks in the wheel...

My amateur guesses are: power steering problem or (can't remember the exact part) but something that has to do with a ball-bearing.

Maybe steering rack going bad.