I looked at: http://www.nfl.com/players/playerpage/313800/gamelogs/2005
To check this.
He had 5.5 sacks on turf (all his home games) and 5.5 on grass (@ SF, HOU, PIT, TEN, SD, ARI (pre new staudium it was a grass IIRC) so I'm not seeing this.
One would suspect he's gonna have more sacks on turf overall since he will play at least half his games on turf plus any away games on the plastic. You also assume that for a speed rusher the crowd noise factor at home is gonna be huge so since home is a beeter chance of getting sacks and home has turf I'd expect some overall disparity but just taking a single season it isn't even obvious that that factor exists.
Where'd you read this?