This is interesting, what if i replace the stock cat-con with the high flow cat-con? any significant difference? Do they sell it here in Malaysia?
Or i just remove the cat-con & connect it with something else, what would be the best? with all else remains the same,will the engine be quieter?
Replacing the standard catcon with a high-flow version will certainly help and has the bonus that it avoids any problems with the annual government car inspections that happen in most countries. Providing there is enough room to fit it, it is a fairly simple/cheap option. Normaly makes either minimal or no difference at all to noise levels.
More popular in the UK is to fit what is often called a 'catcon bypass' section of pipe. This name is slightly misleading - it dos'nt actualy 'bypass' anything, rather it is a section of exhaust pipe/s that directly replaces a removed standard catcon. Usually a socket to take the lambda/oxygen sensor has to be included in the pipe. Even with retaining the standard manifold and exhaust, the results are always good. Any differences in noise levels are harder to predict, but will be modest if the standard exhaust/silencers/mufflers are retained.
Advantages are that it is simple, quite cheap, light in weight, easier to change-over and less restrictive than any catcon. Downside is that it will fail a 'visual' government inspection, so has to be changed-over at test time. However, it has been shown that most engines that are in good condition/well maintained can still pass the actual exhaust emmisions tests without the catcon, (certainly upto Euro/Step3 levels) - depending on how harsh the local set limits are in any particular country.