will there be a difference in exhaust sound/pulse from changing the stock pipe, from exhaust manifold to muffler, to a 2.5" pipe with aftermarket muffler? coz my car idles with a funny sound. when i first start the car in the morning it idles fine with a vroooooooooooo.....sound but after a few kilometers of driving the idle sounds like vroo-vroo-vroo-vroo-vroo-vroo....the sound is uniform and no increase or decrease in the exhaust sound and when i left off the gas to change gear, i could hear my exhaust sounded like a motorbike. what causes this pulsating sound during idle? is this a normal idling sound for a b16 with an hks filter but with a 2.5" pipe? and what causes the motorbike sound when ever i decelerate? thanks.

 

I'm guessing it's your EGR valve has a leak. I dunno