The injectors aren't the problem, it's the valves. And it's not a problem until you have AT LEAST 60k miles. If you want to clean the injectors, just throw some Seafoam in the gas tank. But at your mileage, there's absolutely no reason for it. Just use a top tier gas like Shell and you'll be fine.
I was offered a cleaning by my dealer when I hit 60k. I don't have the M3, but I will likely just use Seafoam before my next oil change. I did that in my old direct injection VW and it worked wonders.
2009 BMW M3 E92 6M AW/FR
Eibach Springs + H&R Front Sway + LUX AE + LCI Taillights + BMW Performance CF Spoiler + Bastuck Clubsport Exhaust