When I had a test drive the other day, I noticed small "puff" sound came out of exhaust pipe every time I changed the gear.
Does anyone notice this sound or cause of this ?

 

i heard the same thing when i was test driving one...

weird.. hopefully it's just due to a restrictive stock exhaust system... and we all know they can't stay stock for long!!

 

are you ref. to the diverter valve sound, sort of sounds like a blow off valve? If thats not what you are ref to the only other thing i can think of is the "burp" that goes from the exhasut when decel.. "Puff" to me is reserved for something that i wont mention here

 

I believe this is caused by the system letting off the gas slightly as it shifts and reapplies it when the shift is completed. This is done for smoothness.

 

It is the waste gate opening to let off the turbo pressure.

 

Eureka!! Thanks! [8D]