Hi. The answer to your question regarding ABS is, nothing. My two '93 240's has that, and tje '88 M-B that I used to own had that, too -- all went through state-emissions testing on the dynomometer without a problem.

But perhaps you're thinking of an anti-wheelspin system? That's a different story. My '90 Mercedes 300E had that (along with ABS), and the feature exempted the car from dynomometer emission testing in my state (N.J.). If it was put on the dyno, the system would think that the rear wheels were spinning (which of course they were) and it would first apply rear brakes to slow down the wheels; if the driver resisted this with the gas pedal, the next recourse for the system would be to cut engine power, too. Bottom line, they can't test a car with an anti-wheelspin system through a dyno emissions test unless they disconnect the system (which the testing authorities won't do, probably out of fear of liability in case their technician fails to reconnect it properly -- imagine the lawsuits!).

Regards