I know this doesn't fix the problem but I wanted to point out: never turn the key all the way off if that happens because the steering wheel will lock up. I'm sure you knew that, but I didn't want to see a member become a smear on the pavement.
There isn't any reason why altering your suspension would cause this, but if you had a shop do the install, they may have screwed with something else in the process. I always tell people that if they have problems after the car has been in the shop, they should at least talk to the shop manager; even if the problem seems unrelated. A lot of shops will just deny responsibility, but some may actually take care of customers. But no one will help you if you've so much as touched the car after they've done work on it (I speak from experience).