Soulflayer has delve and reads
If a creature card with flying was exiled with Soulflayer's delve ability, Soulflayer has flying. The same is true for first strike, double strike, deathtouch, haste, hexproof, indestructible, lifelink, reach, trample, and vigilance.
Winged Sliver reads
All Sliver creatures have flying.
My question is... does Soulflayer gain flying if a Winged Sliver that was in the graveyard is exiled?