Hamza..is the issue fuel efficiency or more hp.
FLI...thanks for sharing your knowledge but i dont agree with you....here is what i know and tell me what do you think.
CC:
Removing a cat may help in reducing the exhaust pressure and will make it flow freely to go a little faster...the downside...your car will pollute more (you didnt respond to this however) this little increment in speed and performance will ultimately consume more gas...even a small bit but still. A Qood quality cat can last upto a 100K level so i cant imagine why one would clog at around 1K mark as it is...unless it is made out of a hollow metal container..lol.
KS:
When you fool the ECU into believing that there is no condition by removing the knock sensor, you eliminate its capability to determine the optimum detonation limit. there may be high frequency vibrations going around but since there wont be any KS, the engine's timing wont be corrected when its needed the most. if this situation lasts long...the engine will be toast.
I am assuming his car has an OBD-II engine, the KS in this case is not just monitoring the engine for optimum peformance but also protects the engine against potentially dangerous and power robbing engine knock. We all know knocking is bad dont we??
Removing OEM parts which a manufacturer puts in is not a good idea. they are there for a reason and there are lots and lots of ther ways of looking into improving a car's fuel efficiency. i dont know this car so i cant be specific but both of your suggestions (CC and KS) will ultimately result in car generating more pollution and not operating at peak performance.
Hamza was not looking for more hp...but more fuel efficiency. the two are inversely proportional.