Our Spiders have a degree of chassis flex, which results in cowl shake and feels like every bolt is going to come out of the car when going over railroad tracks. (This is true for all older convertibles.) You can stiffen the chassis and improve the drive dramatically by installing a chassis stiffener. These are available from the person who designed it, Don Ereminas
, and the usual Alfa suppliers, like Centerline
. (Don supplies them both.)
Now don't confuse the mention condition with the car drifting... One has nothing to do with the other, and drifting is not normal (you are running with very wide tires, are yuo?), so do follow Bob's previous advise.