96 626 injection problem?

I have a 96 626 that idles fine, but whenever I first give it gas, it dies a little and shakes alot then finally starts reving up. Id does the same in drive. I press the gas and it seems to take almost 2 full seconds before it starts dying and shaking then starts picking up, and recently when going at regular speeds it will sometimes just act like the I am letting off the gas then goosing it, then letting off, back and forth

Is the check engine light on. A fuel pressure missfire should trip the light. It may be a mass air sensor.