You didn't replace fuel pressure regulator, did you?

You should probably replace fuel pressure regulator every 150k km or also, it's cheap and easy to do.

My V8 400E gets better mpg than yours

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99 BMW 540i 6-speed 110K Km
03 SAAB 9-5 wagon 80K Km
92 400E (Sold) 245K km
Still missing the days with the Benz, it kept me busy.