I have a 1.3L Skoda Felicia, (carburetter engine without catalytic nor other gimmicks). Since past 1-2 months I would hear the exhaust sound has changed, it became more and more audible and at full throttle it sounded like a spitting with your tongue between lips (kind of like buzzing?). Recently, in past several days it started to change and gained additional bass and overall pitch has become more like a tractor. All the sound effects kick in after 1500-1800rpm and throttle more than 20% open. If I drive smoothly the exhaust almost not audible.
From what I know my exhaust consists of 3 parts (Y-pipe from engine and 2 resonators connected with pipe). Y-pipe looks quite rusted, but holds ok and I doubt it would degrade in described fashion, but maybe I'm wrong.
Here's the question - what part of my exhaust needs changing and how could I verify/check it without garage nor extra tools?