The N/A engines don't have an ALDA, they have an ADA which is supposed to correct the mixture for altitude differences. If it is stuck for some reason, it would certainly stand to reason that the mixture could be richer than it needs to be.

All other things being equal and all options being exhausted, you could always tweak the max fuel setting of the IP to lean things back out.

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Current stable:
1995 E320 157K (Nancy)
1983 500SL 125K (SLoL)

Gone but not forgotten:
1986 300SDL (RIP)
1991 350SD
1991 560SEL
1990 560SEL
1986 500SEL Euro (Rusted to nothing at 47K!)

Gone and wanting to forget:
1985 524TD 167K (TotalDumpster™) [Definitely NOT a Benz]