really all you can do in such a case like that is check out what all would make it misfire. Check your plug gap( make sure it's with in spec ) check your wires for burns/breaks. Check your cap and rotor( make sure the points look good, and the rotor tip looks good ) check that your getting power to all of your injector plugs, while your doing that might as well check your fuel pressure, make sure it has enough. if all of that is said and done and nothing seems out of place, I'd just replace your injectors, or have them cleaned by an injector company. sounds to me though a good tune up is in order.

a good way to tell if your injectors are working properly is if you pull out a spark plug and notice the condition that it's in. if it's super dry and white, obviously no fuel is entering the combustion chamber. also if there is a check engine light. Make sure to get that checked out too.