Not knowing much, especially the year and engine. The first thing I would do is a computer diagnostic to see if it's throwing any codes. The next thing I would do especially from what you've said is more of a pre-existing issue than a new one is clean out the intake system as much as practical. From the point of airbox entry to (and inside of) the throttle body. There is so much in that chain that gets nasty. AIR is the most important part of the combustion process, granted there's no 'bang' without the fuel part, but there's no 'bang' without the air either. The computers in these things over compensate for way too much IMO, so you could find yourself chasing things around. Make sure the basics are in place, air & fuel.
