Question about split duration cams in turbo engines

[Darth Fiero]

I was browsing thru the Comp Cams catalog and noticed some of the cams they offered for the Buick GN. Most were single pattern cams (ex: 212/212 duration @.050) but I also noticed a split duration cam with more duration on the intake than on the exhaust (218/212). What is the reasoning behind this? Most of my friends with turbo buicks are running cams with more duration on the exhaust than intake. I am just curious what this (more duration on intake than on the exhaust) does for drivability and performance.