knocking sound (or pinging) is very hard to describe.
if you can hear a metalic sound or if it sounds like "shaking a can of sand/marbles" or a rattling sound ...when u accelerate your engine, then your engine is knocking.
i am thinking to mod to straight flow for my Na Altezza(6MT), is it worth to do that? any other thing can improve my power besides of modding turbo or supercharge. i dont wan mod a lot, if possible wanna keep it...