Trying to solve an Engine Problem.
 

Owner of a 2005 Chevrolet Cobalt 2.2L LS, since it's purchase in 2005. I am new here.

This car as had a few problems since I have bought it, but nothing that couldn't be found on a forum or mechanics help site. But this has really got me stumped.

a few days ago coming to a stop light I noticed the engine acting alitte erratic, just alitle bit. Being the owner of this vehicle for it's life span I know how normal Engine operation feels. That being said, there are no lights on the dash and no codes that have popped up, it's running on all four cylinders, not lacking in power, starts up just fine, but the engine just seems alittle rough or slightly erratic.

Not sure if this has anything to do with it, but I did the oil change myself and put in Royal Purple Synthetic oil at specified weight. I did try a few things some other forums have posted on similar problems ie: clean Throttle Body, Nodes, check for corrosion on electronics/wire/clips, etc.

Car still runs fine, just slightly erratic. Doesn't seem like a major problem but could be one that if I catch it early and won't develop into anything worse. any idea's? I am leaning toward Oil, Spark Plugs (Which were changed recently), Coils. But Like I said, I have operated the vehicle for a long time now and can feel any thing out of place with the normal engine operation. Any help would be appreciated. Thanks.