UPDATE: NGK website has bad info on it, see post below from Robby363 that get it right. Info on Cabin Air Filter is still useful

I've been doing some data gathering trying to figure out some maintenance parts for my SRT-6 and I happened upon the follow discrepancy between SRT6 and SLK32 spark plug specifications.

Ignoring the difference between the "I" and "P" at the beginning, which denote Iridium and Platinum respectively, the SRT6 plugs call for a 5 heat range with a 0.044" (1.1mm) gap, while the SLK32 (and C32) plugs call for a 1 step colder plug with a 0.040" (1.0mm) gap.

SRT6 - PFR5R-11
SLK32 - IFR6D-10

Anyone know why Chrysler specified hotter plugs with a smaller gap than Mercedes did for the C32/SLK32? Increased service interval? Something to do with pollution control? Reliability?

Is this a clue to often debated (but not yet put to bed, I think) debate on why Chrysler rated this powerplant at 19hp less than MB?
________________

A good looking part deal I found poking around the web :

GermanAutoParts has a great price on the OEM Micronair Cabin Filter - I paid almost as much for the WIX, and its construction wasn't anywhere near as impressive as the OEM Micronair filter.