My experience with CATCON is as follows (this is a more detailed response):
I had new Corolla. I used to fill up at F-11 Attock pump in Islamabad, as it was near my house. After 40,000 KM mileage, I noticed that the car was not climbing Salt Range hills on motorway with full power. Later when the mileage reached 52,000 KM, The car climbed Salt Range hills with great difficulty. Moreover, It could hardly reach 120 KMPH speed on flat stretches of motorway. Fuel consumption increased by about 25%.
On returning to Islamabad, I showed to self-proclaimed Toyota expert in F-11. He advised to change the clutch. Another mechanic said problem was with tapets. I didn't believe them; did some research on Internet and went to Imran Silencer Walla, located at Sariya Chowk, G-8 Islamabad. He disassembled the silencer, exposed the CATCON, which was totally choked with an Orange powder. He then cleaned it by blowing high pressure air in reverse direction of exhaust flow i.e. back to forward.
After re-assembling he asked me to check it out. When I did test drive, the original power of the engine had returned. Later on Salt Range hills the car climbed effortlessly. Problem resolved.
After that I never filled up from Attock pumps. Always from Shell. The car has now done 120,000 KM. No more signs of a choking CATCON.