Why does my car stumble when I increase RPMs?

Sounds like you might have a plugged catalytic converter. If it is, the exhaust at the tail pipe will sound more like a hissing instead of the normal "putt putt" sound. If you work the throttle under the hood, you might hear some popping through the intake / throttle body, especially at higher speeds.

A failing MAP sensor can cause bogging too. On the older cars from the late '80s and early '90s, it commonly caused the engine to stall when the accelerator pedal was held steady. The engine would continue to run, (poorly), as long as the gas pedal was moving. That sensor can fail to report the correct manifold vacuum readings but as long as its signal voltage stays within its acceptable limits, (0.5 to 4.5 volts), no fault code will be set. A quick check for the MAP sensor is to disconnect the plug. The Engine Computer will recognize the failure and substitute a known good value to run on based on approximations from the other sensors. It still won't run well but if it runs better, suspect the sensor. The MAP sensor has the biggest say in how much fuel enters the engine.

Not routine. My rusty trusty '88 Grand Caravan with 230,000 miles still has the original converter and it's working fine. I don't know what causes some to become blocked and others don't. Leaded gas will do it but you can't find that anymore. Overheating it is probably more common. That melts the substrate into a block the exhaust can't get through. Overheating is due to too much raw unburned fuel entering the exhaust system. That is monitored by the Engine Computer on '96 and newer models and will result in a flashing Check Engine light when it's severe. Even a slightly too-rich mixture will eventually be detected by the computer resulting in a stored diagnostic fault code and the Check Engine light turning on.

In the absence of overheating, I suppose it's possible for the catalyst material to crumble apart and cause blockage. I never autopsied one to see what happened.