Do I need to clean or prep the mounting surface before installation?

Yes. Scrape away old gasket material and carbon buildup from both the manifold and header flanges with a gasket scraper or plastic tool. A clean, flat surface ensures a proper seal and prevents leaks down the road.

Will this gasket work with an aftermarket header, or just the stock manifold?

This gasket is designed for factory header applications on the 2.5L. If you're running a custom or performance header, verify that the bolt pattern and flange thickness match before committing to installation.

What's the return window if the gasket doesn't seal properly?

Contact ModSupply customer service with photos of the installation and any leak location. Returns and exchanges are handled case-by-case based on fitment verification and installation method.