2001 Tahoe-Irregular idle

My Tahoe just started this really odd idle issue in the last few days. It seems to rev up for a few seconds then let down and repeat. It does this when warming up. But the BIG issue is that after driving down the highway at a higher speed when I come to a complete stop while setting still it really revs up and down. I'm afraid to take my foot off the brake that it would take off without even the gas pedal pushed down. Is this a fuel pump or filter issue? Or something else?
Any help would be greatly appreciated