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Like all modulars, the Coyote uses exhaust manifold studs, not bolts. Enlarged to 10mm from 8mm on the 4.6, the Coyote studs are larger to resist shear loads from shrinking headers. After thousands of heat cycles at high mileages, the manifolds can shrink and pull on the studs, something the 8mm stud apparently can't quite handle. Also, the nuts are prevailing torque pieces and carefully torqued to less than maximum clamping load. This allows the manifold flange to float slightly when glowing hot, retaining a gas-tight seal and not shredding the gasket or overly stressing the manifold. The prevailing torque nuts also resist turning by the ballooning hot manifold. Now you know why your 4.6 header bolts are always coming loose.