Sounds like a throttle body gasket or an intake manifold leak. Check all of your vacuum hoses, there's a diagram under your hood that maps out where everything is supposed to go.

My car did this when my evaporative purge solenoid hose came loose. It jumped up about 1000 RPMs and at first, I couldn't feel a difference in the way the car ran. It didn't throw codes in the ECU even though my A/F mixture was way off.

Other vac hoses to check... PCV and Brake Booster. Make sure they're not hardened, cracked, or punctured.

Good luck, I hope it's something simple.