mk2 astra running problem?

i've got a mk2 astra 1600cc carb, just had it restored (mainly bodywork), passed it's MOT no problems. Since i've had it back from the garage it seems really "flat", best way to describe it is as if the brakes are binding, which they are not because the brakes are okay and passed MOT. Feel it could be blocked carbs, have been advised to use some Redex in the next tank of fuel but other petrol head friends say redex doesn't do much. Put a new air filter on which hasn't cleared the problem, it used to be quite nippy (i know it's only a 1600) but i reckon a 1.0L micra would kill me at the moment!!! Idles ok, revs through the range ok, Ideas on what it could be?