Do I need to clean the flange surfaces before installing this gasket?

Yes. Scrape off old gasket material and carbon buildup from both the header flange and manifold surface. Use a gasket scraper or soft wire brush—don't gouge the metal. A clean surface seals better and lasts longer.

What torque spec should I use when bolting the header back on?

Refer to your vehicle's service manual for the exact torque specification. Tighten in a cross pattern to ensure even clamping pressure and avoid warping the flange.

Can I reuse the old bolts, or do I need new ones?

Header bolts are typically reusable if they're not stripped or corroded. If they show rust or damage, grab a fresh set—they're cheap insurance against a leak or seized bolt on the next job.