first, go back to the shop and ask for your money back. they failed to fix your car. if you can't get a full refund try for a refund of the labor. you may have needed the parts they sold you but they said it would fix the problem and it didn't.
it symptoms of the problem are pretty well hidden in with the other shop ''issues'', especially the issues that caused you to go to the shop in the first place. but....
look for a vacuum leak. the small vac lines / tubes running from the engine to the passenger strut tower. or the large one going from the IAC to the plastic air plenum . it attaches to the plenum on the very bottom, underneath and is very hard to see.