The taste totally depends on the mango used. If the mango is raw, then it would be sour, but if it is partly ripe, then it would have a lovely tinge of sweetness too.
Do not overroast the mustard and fenugreek, otherwise the whole kadumaanga would turn so bitter that you won't be able to salvage it at all. So heat the pan, switch off and then just roast on the hot pan till the pan cools down - if you are unsure of burning it.