I think as long as a tune doesn't destroy your engine and transmission, go for it. You can certainly enjoy the extra power at legal speeds. Given the 213 is AWD, it can probably handle the torque and make the car more fun..it is hugely capable. Get it on a good road and you can be within the speed limit and I certainly used to kickdown my c63s a whole lot on my favourite roads in Wales eg the A482 where you can have raucous fun without breaking the speed limit or driving too dangerously.
When I was getting my exhaust done at MSL there were 4 chaps, all looked like they spent far too long in the gym, each with their own amg, I spoke to one chap who has had many cars tuned including his current car a w213 e63s and he was very happy with what MSL was doing. He was on stage 2 on his car and the exhaust sounded ferocious and he mentioned the 213 had some inbuilt engine protections in the software so it is harder to get crazy numbers but at theHi , have a fee same time there's good engine management protection which is difficult to bypass or something along those lines. He was getting over 1000nm and I think the HP was well over 700.
I didn't actually get to go on my fave roads as the Mrs said no to letting me escape for a few hours. I'd be very surprised if the A482's limit will be changed. Its not popular at all, doesn't have any nice views, it's just left , right x100 corners one after another and wide enough to not be concerned about oncoming traffic.
