That is just way to much timing for a m104. Max timing at 100 % load should not really be more than 21-24 degrees. Put it on a dyno to verify. I am supercharged but regardless I see absolutely no gains in power past 16-17 degrees of timing. And very little past 15 degrees. Factory timing is about 18-19 degrees. When I first started tuning I saw major detonation at anything up in the 26-28 degree range at full load. That was n/a. Also the Mercedes knock sensors do not read the same as an aftermarket. It takes a significant amount of knock to trigger a signal on aftermarket ecus. I finally gave up on the Mercedes knock sensors.
Bottom line is I would really recommend pulling a lot of timing and putting it on a dyno to see what the motor likes. Most 4 valve center spark plugs do not need a lot of timing.