N20 Engine, F30 320 vs 328

[G37Sam]

I hope this isn't a repost, looked around but couldn't find anything.

When looking online, I found out that both cars are using the same N20B20 engine. How come they're 60hp apart? Different size turbo or just a different tune?

[Ayham]

Maybe more efficient turbocharging, better mapping, and intercooling.

[SHkater]

I've read on this a week or so ago, don't remember where though. It was mentioned that the 320s engines internals differed a little

[G37Sam]

From what I read (could be wrong), they're using the same bore, stroke & CR