Mitsubishi Repair: mis firing, distributor cap, spark plugs

Question
Hello Anthony, hopefully you can help me even though it's not an Eclipse.  I have a 1989 Galant, manual tranny.  It was misfiring so I changed all the wiring from spark plugs to distributor, and in the process of changing the plugs I found out that one of the tips on the old spark plug was missing, so I thought ok problem solved.  I took it on a test drive and it ran perfect, woke up the next morning to go to the store and the problem is back, could it be the distributor?  

Answer
Mark,
I would first pull the spark plugs again to see if any have any damage to them.  If you find another spark plug with a broken tip, that could indicate the cylinder is over extending and breaking the tip.  

But if the plugs look fine, it can't hurt to replace the distributor cap and rotor.  Those items are inexpensive and easy to replace.  I would highly recommend you buy the new cap and rotor from the dealership to ensure a perfect fit.
Good luck!