I'm a 335i owner. 70k miles and turbos already replace when i bought it.
Had to rewire the thermostat heating element as someone had crimped the wire (took like 4 hours) and 4 new goodyear f1's have set me back ~£500
It's a cracking car though. Mine came with jb4, Dual Cone Intakes and Catless downpipes. Dyno sheet for 400hp. I don't think you could go much faster for less. Getting the intakes Walnut Blasted by Turners (twickenham) next week and hopefully an Oil Catch Can for xmas.