Again, depends on exact use. If you don't want weight over the rear wheels, so you use a light fuel load, you will probably notice benefits with fuel delivery (obviously, it would be pretty constant). But I'm not sure how many people actually run light fuel loads when drifting, so it then becomes more of a preventative thing by having the foam.

The only reason race cars use them is to prevent surge with low fuel loads and on tracks that have elevation changes. I've tried looking for pics to put up but I had no luck