it's psychological! the reason why you're feeling sluggish b/c our brain, expected that the car would be riding smoother, faster, and better, etc... after the service. but since that's not how things works, instead the expectency of our brain to the object making us thinks that the car is sluggish. but really... it's the same! servicing/repairing the car doesnt make it go faster after it was used and have more than 5000 miles.
i know this b/c i've changed car's oil every 3000 miles. everytime when i get the oil changed, in my mind im expecting the car to go faster and smoother. but instead i felt sluggish. b/c the car still runs the same, so it opposits of your though.
get what im saying?