I have Akra titanium (oval) slipons for my 900 (2004) which are definitely loud at and above about 4000 rpm, and are accordingly marked "not for road use". Lovely bits of metal, and the new bass "voice" (never mind the volume) that they give the bike is stunning. Have been a bit nervous of the local plod, though, and accordingly tiptoeing around at low revs when near civilisation. Not tried them on a long run yet, but I don't imagine they'd add any noise burden for the rider (Can't speak for pillion), especially over the old wind/turbulence issue. Mr satnav has carbon ones, I believe, so will probably comment. Can't guess whether Japanese views will be a problem - they seem to be such a mixture of officiousness and the opposite that it's hard to tell. The outlet pipes being 48 mm internal dia, DB killers from Staintune should fit, if you don't mind drilling holes in the cans' outlets

for the grubscrews. I have a pair, but they need a bit of engineering as they're just a shade too tight - the outlet welds seem (pun?) to be the issue, and so it looks like I need to grind a groove in the DBKs to suit. (Hopefully the ugly sods will then slip in out of sight - they're not a patch on the Serbian work). Hope this helps
PS I have friendly neighbours - so far.
Wondering if any AKRA users can do me a favour. After a low speed collision, my right Akra titanimum needed replacement (no other damage TG). The local shop ordered a pipe from the distibutor - but it's comes in at 47 cm - 4 cm longer than the one that got crushed (and the one on the left. How long are your pipes (outside of strap to outside of strap)? I can't seem to get an authoritative answer from the guys here in Singapore, nor the shop in Amsterdam where I bought them. If 43 cm is the correct length I may be able to do a swap.