Just a data point.... I purchased my 05 in 2010 with 130k on the clock. It now has 229k and 99% of those 99k miles were on homemade BD.

Mine still accelerates like a bat out of he** just like it did the day I got it. I won't even let my 16yr old son drive it because of the acceleration.

I recently had some shifting issues, so I sprung for the aftermarket tranny dipstick and did fluid and filter change. Back to normal health now.

During some of my shifting issues, it was evident that the tranny seems to have the ability to restrain the engine. You may want to look at the tranny as a contributor to your problem.

On BD, I will get 32mpg all day long. The very rare occasions of pump diesel, it will get 37.

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Mark in MA
05 MB E320CDI 402k Granite Grey Metallic
05 MB E320CDI 267k Black
05 MB E320CDI 232k White
05 MB E320CDI 209k Tectite Grey
99 Dodge 2500 Cummins 5sp 148k
62 Jeep CJ-6 120k