Can I wrap this around existing spark plug wires, or do I need to remove them first?

You can wrap directly around installed wires without removal. The 6" segments flex enough to fit around wire bundles and boots. Work methodically section by section and overlap wraps slightly for complete coverage.

Will this wrap affect spark plug wire or boot performance?

Thermal wraps improve wire longevity by reducing heat exposure. Make sure the wrap doesn't compress or kink the wire itself — thermal protection works best when the wrap sits around the wire without restricting it.

What holds the wrap in place during engine vibration?

Installation method not specified — you'll need to test-fit before committing to cable ties, adhesive, or a combination of both. Most builders use stainless steel or high-temp cable ties for secure vibration-proof hold.