I've got a lot of play in the steering when in a neutral position (going strait).

The ball joints were replaced about 10k mi ago and the wheel bearings seem to be snug. A few months ago my rack died and I replaced it with a used one from a junk yard. After install, I took it down to have the alignment done and when I picked up the car the mechanic that did the alignment (and put new tires on) asked if I did the rack myself. He then complemented me on the great job I did (patting myself on the back).

A month later, I started to get a lot of play in the steering. And now, having driven a month on it, I noticed some unusual wear patterns on my new tires.

PS fluid level looks good and the new* rack isn't leaking.

What do you think are the culprits and what should I check before I go back to the same shop and tell them that the alignment is off and ask for a warrenty realignment?

Thanks