why? bhaap se "kileen/champi/safaai of a thermal reactor?"
to keep cat converter in good shape, just drive normally, - the ECU is tuned to start/ignite it keep it in good shape forever, meaning the ecu should not be dumping fuel in the engine or driving with a severe ignition misfire (even to workshop), or have the wrong engine oil in it, or using the wrong kind of RTV as engine sealant, or driving with a blown headgasket.
In countries and areas where an exhaust inspection is mandatory for car to pass for road worthiness, they dont check for "flow" or "pickup" - but put a sniffer in the exhaust and make sure the cat is actually working. In some older model cars its normal for the owners to run the engine near redline for a few long bursts of acceleration to thoroughly heat up the cat which makes it pass emmissions easily.
cold/cool cat doesnt work, - this is why modern ECU are pretty rich when the engine is cold, the rich fuel mix forces the cat converter to "ignite/start" quicker.
Please stop believing in the "motorclean/steam/bhaap" manjann.