Fabric and Leather Chewing
Wool chewing falls under the realm of OCD and is covered here.
For the kind of chewing behavior we're discussing here, the best way to discourage such behavior is to offer other 'legal' chewing sources for your cat, e.g. chewable soft toys. I've even seen wool mice, which might be a perfect substitute for your mohair sweater. Other cats will chew on leather gloves, or even shoes (rubber flipflops come to mind). Jaspurr loves to chew newspaper. He doesn't eat it, he just rips off small pieces and spits them out, and soon is surrounded by newspaper confetti.
If you can't put away all the fabric and leather items your cat likes to chew on, try the bitter apple spray on the area where he usually chews, but test it first on a small hidden seam.
A Word About Kittens' Chewing
As mentioned above, kittens often chew because they are teething (around three to six months). All of the methods described above will work, especially the toys, but there is one free tip that works wonders with kittens' teething: plastic drinking straws, especially the large ones used for milk shakes. They provide the crunchy contact kittens need, and they make a great interactive toy. Some of my forum members will tie a loose knot in a straw to add interest, but I prefer to leave them straight. You can derive lots of interactive play by teasing your kitten with the straw, then let him "capture" it and watch him proudly carry around his "prey." Our adult cats still remember their straws, and it's not unusual to see one of them batting one around the floor.
Here's to healthy, legal chewing for our cats!