Acrylic doesn't block like wool. If your pattern is mostly stockinette stitch (knit a row, purl a row) with the eyelets in it, that's your problem. Stockinette curls and it's not a big problem with sweaters because you sew the edges together. But in a scarf or wrap, the pattern needs to include garter stitch or seed stitch on the edges to keep them flat.
There's a FAQ at the top of the How To section that discusses this.