Thanks Super-DA9 for such a prompt reply.

I have recently installed new extractors one month ago so there is no hole or leakage in piping, yes leak in exhaust can be the reason i will check it because now a days i am feeling noticeable change in exhaust sound, sounding a bit rough.

And air intake is not that deep, it is fitted in place of stock box with a welded metal piece. and i think on last service filter was cleaned with vacuum and blower to catch the dust, CAI is around 2 years old once i asked my mechanic to change the filter he said this is for once in a car life unless broken.

With B16A2 gearbox installed in my car first 3 gears pulls very hard but later 4th and 5th usually take some time to build the rythm. Could you tell me what is the difference between gearbox of DC2R and B16A2(i have s80).? and could gearbox of an integra DC2R be match with B16A2?

One of my mate's was suggesting me to change the intake manifold and spark plugs what do you recommend?