I have a 2001 CRV with around 155000 miles. The engine pulsates when RPM reaches above around 3500 RPM, and when the car is under load such as going up a hill. I can get the pulsing to happen with the car sitting in idle just by revving the engine. When this happens, there seems to be a lot of pressure on the exhaust system. I can actually see the catalytic converter being pushed back by pressure, and exhaust gas being pushed out between the front of the converter and the pipe that connects the converter to the exhaust manifold. What could be causing this?

This car was in a front-end accident recently. I made the repairs myself. The distributor was damaged but I missed it during the initial repair. There was a crack on the bottom of the distributor cap that I didn't see. The car ran without problems for a while until one day it just suddenly stalled and wouldn't start again. There was no spark. I saw the damage when I checked the distributor. In addition to cracking the distributor cap, the accident separated the igniter from its heat sink. I'm actually surprised the car ran at all with these damages. I think the igniter eventually overheated and died. I decided to replace the entire distributor just in case there are other damages in the original distributor. I did my best to install the new distributor in the exact same position as the old, but the timing marks on my engine is so faded that I had problems checking timing with a timing light But the engine started and seem to run fine, so I think I'm at least close with the timing. The pulsating started shortly thereafter. I speculate pulsating has nothing to do with the new distributor, but not 100% sure. Any opinions?