As Ross Bentley says in Speed Secrets...make the car show its weaknesses. At that point, I think its optimal to mod. I went overboard on my 330 but being more judicious with my M3. I have added camber plates and BBK to address obvious shortcomings.
Everyone, thanks for the info. Basically being a cheap skate doesn't pay here.
If I do add downforce does that wear the tires a lot faster?
2015 F34 328iX GT Glacier Silver
2011 E90 M3 Monte Carlo Blue
2004 E46 M3 Imola Red