Same as mine. Warped rotor or both rotors on the front.
Pete

Warped rotors, not really badly warped yet, but will get worse.  Check
rear brake adjustment, given 7 years old, check condition of brake
hoses ie flex lines as well as
the cailpers moving freely on their slides.  Push pistons in with
bleeders open, and
then see if caliper moves freely.. If hard to move, get a caliper
hardware kit. less than
$2 at autozone and install them.  Lube pins and bushings with a high
temp silicone lube.
little bit goes a long way. Clean the slides the pads ride on and lube
with thin coating of
high temp moly lube.
If this thing has rear disc, make sure the calipers aren't froze to
their slides, look for uneven pad wear, major  wear on  inner pad then
the outer is indicatior caliper housing isnt moving.

I would assume if the tires were replaced the shop checked the front
end for worn parts, they usually do looking for add on sales.  However
GM's are hard on idler arms, actually GM specs allow for a termendous
amount of movement before condemning. I only use Moog, their design is
totally different than GM's and a major improvement.. Badly worn a-arm
bushings, but again you should have had wear patterns on front tires
becasue alignment would be out as well, and usually you get a pull
when brakes first applied if they are really bad maybe even a thunk.

Whitelightning