dont think you can chip the 85 either.
one thing to make any car faster is help it breathe. larger intake, larger output - interpret that however you can cause i dont know where to find eta parts or what is interchangable. you might check out 528e parts, i dunno.
oh, not to mention tune the engine if it hasnt been done in a while (new filters, plugs, wires). another thing you can do is find a higher ratio final drive. you will lose top end, but its one heck of acceleration difference. Lastly, drop the weight of your car (but that one is hard to do sometimes).