i have a EL (Auto) and its nice through the rev range and smooth comming down but my mate has a series 2 AU (Auto) with a redback and his has a nice crackel comming down what can i do to get that crackel

I've had a lukey exhaust in a vl 6yl. It sounded awesome really nice crackle when down gearing. I to have searched for the question you've asked the common answer is they'll sound almost the same.
If there the ones from eBay there made from mild steel and roughly look the same and are priced within each other so both should be good. I'm ordering a lukey cat back within the month.. Should be good!