Volksagen VR6 coils packs are well-known to develop cracks leading to engine misfires. Marc Gallagher wrote up an excellent repair guide that involves coating the coil pack in epoxy.

At ~50k miles, my GTI VR6 developed the classic symptoms. I wanted to find an epoxy that flexible, bonded plastic and had a wide temperature range. I settled on 3M Scotch-Weld 2216:

"Highly flexible epoxy provides a high-strength bond with excellent resistance to peeling and high shear strength. Bonds rubber, metal, wood, masonry, ABS, PVC, acrylic, nylon, and polycarbonate. Temperature range is -67 to +350 degrees farenheight."

Those looking for an "industrial-class" epoxy to patch their coil-pack may be interested in this route.

One-Year Update: After one year and approximately 8k miles, I've had zero problems.
Three-Year Update: Still going strong; no problems with the coil pack since this repair.

Picture of the epoxied pack: