Ah, HPTuners. I haven't heard that in a long time. I have an Fbody cable around here somewhere...

Unless something has changed, everyone on E53 is using a complicated mess of bootlegged OEM software. "ISTA" of some flavor, and some other packages that do things I don't remember. I don't know what your ECU is, but the 3.0 is a siemens unit (MS54) shared with E46 3 series. Those folks (e46fanatics.com) did all the work on learning to code and tune for 3.0.

If your ECU is the same, those packages should work for you.

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2001 E53 3.0 5pd