whats wrong with my car!

i got my car back from the shop yesterday. all they did was replace the coolant hoses and fix a leak in the exhaust and put on a new valve cover gasket. but for some reason, my car is MUCH quieter and EXTREMELY slow. i used to time it at around 10 seconds 0-60. now it takes 13. most of the power change is at low speeds, it seems like the car just won´t pick up like it did before. it also seems slow to respond to slamming the pedal at higher speeds, but there doesn´t seem to be a power loss there. what could be wrong? my dad doesn´t seem to think there´s anything wrong, but i know there is, and i don´t want to take it back to the shop. please help!