Why would my 2001 Staurn LW300 3.0 Ltr. act like it is hesitating while I am driving if I just replaced the spark plugs and the fuel filter

What is your question?

My 2001 Saturn LW300 seems to be hesitating when I am driving, I have recently changed the spark plugs 2 times (the first ones where the wrong ones for it) and the second 6 spark plugs I put in are just like the same ones I pulled out (double electrodes) but not what the repair manual says it should have. Simply because no one in my area (all the auto parts stores) seem to carry what it states in the book. I have also just recently replaced the fuel filter. The day that I had these repairs done the "Check Engine Soon" light went out and stayed out the entire day. And was running absolutely great. But within a day the "Check Engine Soon" light came back on and 2 days later it began to hesitate while driving but was not doing it all the time - every day. It would run fine one day then the next it would start hesitating again, and it continues to run like this. However I have began to notice that it gets a little worse if I am driving at night. The repair manual tells me nothing..

What makes this problem better or worse?

Driving at night it seems more prominant.

How long has your 2001 Saturn LW300 had this problem?

A couple of weeks now.