Is the car "stuttering" as in, you can feel vibrations/shaking, or is it just hesitation. If it's hesitation, I would check into replacing your fuel filter. Hesitation can be derived from a dirty fuel filter. Because the filter is clogged, fuel can't be delivered as efficiently as it should be, thus creating an unequal fuel/air mixture. The CPU then sneses this and pulls timing, thus causing the "hesitation".

I would also look into a boost leak problem, as already mentioned. Make sure your I/C Pipes are tightened down good, BOV is sealed off well, intake pipe, etc. Since the car has been sitting for a long time, the I/C pipes may have detiorated and may have a leak or crack somewhere.

Bad gas is a possibility too, but I doub't it would cause the hesitation in certain RPM ranges.