Why is my car lagging?

Without codes or any clues like climate, we will be limited here. We'll need more information like your climate and if you scanned the car, to give you an idea. Get the car scanned so we have more to work with. A scanner like this is plenty for you. Same as before, but offers bidirectional control.

The first thing I would check is the air filter. Have you changed it recently? If not, and it's more than a few years old, I would go ahead and try that first—NA engines and clogged filters do not get along and will behave this way. You can probably find this from your local auto parts store - this will run you $10-20.

The next thing I would look at is the MAF sensor—again, a bad MAF will do this.The quickest way to test this is to disconnect it, drive the car, and see if it behaves any better. If it does, then you have confirmed that the MAF sensor is bad.
NOTE: This test will trigger a CEL code, so get a cheap scanner before trying this. In addition, without a MY, we can't locate the part# for you - in lieu of a MY to locate it, search this: "XXXX(MY) Malibu MAF sensor".