In a typical OE setup, the Johnson CM30 pump will lower IATs ~10 degrees Fahrenheit.

Reputable source…http://www.mbworld.org/forums/showpost.php?p=2376178

When getting after ‘em on a road course, or especially before fitting an aftermarket pulley, upgrading one’s heat exchanger is imperative for best performance. The DME will retard spark timing significantly, and dump fuel, once the 140 degree threshold is breached and continue to do so as temperatures increase. Properly controlling heat soak, high IATs, and their attendant ‘dialing back’ from ideal spark timing and mixture strength parameters will measurably increase performance.

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