Check the service records and see what has been done to it.

I had a 535i. Had a HPFP fail early on (2008). Reduced power mode, drove it in to the dealership fine. It only had the power of a 528, but it wasn't a big deal. No further issues. Flash forward to 2011. Went in for the last prepaid oil service. Dealer said there were two campaigns to do on it. I hadn't received letters yet, but he said they would be coming shortly, and they could do the work then. Got a new HPFP (latest generation, new supplier). No problems prior to change, but it responded more crisply after (likely software). Dealer says they have seen no problems after the latest pump came out. They are doing all of them, pre-failure, and there is still the extended 10 year warranty.

I wouldn't hesitate at all to buy another 35i.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue