Upgrade petrolers to Euro 6

Moin, there is always talk of diesel conversions. What does it look like with the petrol engine? A conversion from Euro4 or Euro5 to Euro6 would have to be far less complex than with the diesel engine. Are there technical possibilities or specialized companies that offer something like this? Because of me also by individual acceptance. Who has any idea? I consider something like this because the cat of my car dissolves and makes rattle noises.