Thick carbon layer in exhaust pipe

Had an even and thick carbon layer in exhaust pipe.

Noticed an even thick carbon layer (2-3mm all around) in exhaust pipe. How to clean it easy way. Car is turbo charged, i think this carbon layer creates an exhaust choke down where exhaust inside diameter becomes smaller and cause more turbo lag and more back pressure. Any best method to clear it up is much appreciated.

you could just do it when the engine is cold and use a steam cleaner they use to clean engines with at fancy car washes

Thanks Mr Scotty