I have the 4.9 litre v8 99 E150 conversion van, about 85k miles, and experience a big cloud of white smoke exhaust when first started, and slight white smoke when warmed up. Uses about a 1/2-1qt of oil between changes; my mechanic (who didn't have time to look at it today) doubts it is pcv since it is white smoke instead of dark, and suspects it could be the transmission modulator or possibly valve stem seals. The trans mod would be about $200, the stem seals about $1,200 because they have to pull the heads. He is not sure it this model has the trans modulator. I trust this guy/shop due to years of experience, but since he doesn't specialize in this engine, we could be missing something. Any help? Thanks!!