I dunno about the chains, rails and such. My M104 IL6 hads 248,000 miles when I opted for a 'maintenace repair' on timing chain and tensioner. Still very quiet at idle and from what I've read here that it not unusual for the M104 IL6. I am assumnig the sportline has the IL6?

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles