Entaran said:Ignition leads are shot.
Check the plugs to see if one of them has burnt an end off.
10 to 1 your leads are sparking against something.
How can you say this is definately the problem. Most fo the time if the leads are ****** it will miss on idle, miss on acceleration and on cruising.....Not just over 3k.
I would say Cat and possibly timing. But as Dre said it could be A LOT of things! its almost impossible to diagnose a problem like this without seeing the car in person.