There are lots of lovely straight sixes out there but as you say when I try and list them I find they are all older models!
RB26DETT Nissan Skyline GTR was wonderful and that was even with turbo/catalyst. It did benefit from an aftermarket exhaust that could fit a full sized hedgehog mind you.
The 3.2/3.3/3.5 out of the older E36 generation of BMW 635CSi was a smooth as butter turbine noise. Not loud or naughty but a lovely cultured sound.
I guess the balance of turbo, catalyst, high HP/Litre and exhaust tuning for back pressure to maintain the catalyst is a serious challenge.
Not to mention the recent changes to drive by noise laws. It is going the same way as Switzerland and we all know how the sidepipes work there
