Can catalyst converters be cleaned

Good evening,

The simple answer is no.

If you have the 420 code, it means the precious metals are worn out and the converter needs to be replaced.

Roy

If its not coming up as 420 code but is running as if converter is clogged. How can i verify?

You could drop the pipe from the exhaust to the manifold and drive it and see if it runs much better.

There is a gauge called a back pressure gauge you install in the upstream O2 sensor. That will measure back pressure. You can get one at a parts store for the test.

Roy