Hyundai Repair: 2000 Hyundai Elantra Hard start, hyundai elantra, fuel additive

Question
My girlfriends 2000 Elantra has been hard to start for about a month.  Starter cranks fine.  Upon starting, the engine sputters on hard acceleration.  I have checked plugs and wires, ohmed fuel injectors, new air cleaner, and added a fuel additive.  No fix.  I took the car to a mechanic and he said he pressure checked the fuel system and that the fuel filter was clogged and he replaced.  Problem still exits and he say he thinks it might be fuel injectors.  Any help would be appreciated.  
Thanks

Answer
If you can tell me, I'd like to know the results of the fuel pressure test.  If low, you probably need a fuel pump.

Also, please tell me how you checked the plugs and wires.  Since most misfires are ignition-related, I'd like to be sure of where we stand so I can determine whether further ignition testing is warranted.

And, while I'm on the inquiring for information bit, please tell me whether your check engine lamp is on.  If so, have you checked the diagnostic trouble codes?  If so, what are they?

I must say that I'm a little doubtful of your mechanic.  A good mechanic will be able to determine for certain whether the injectors are the issue.  Furthermore, the test results that indicate that the fuel filter may be the issue are different from the results that indicate that the fuel injectors may be the issue.  So far, it looks like your mechanic is heavy on guessing and light on diagnosis.