Ace A350 exhaust manifold clearance fix
 

It’s a great header BUT annoyingly it sticks a little low by about 1/8” or 3mm, contacting the aluminum panel and making the car sound and feel like it lost a cylinder. Here are the two magical places on this panel to either flatten with a hammer(they are raised reinforcement ribs) or potentially drill with a 1” hole saw. Notice contact points circled with a marker in the pictures.

EDIT 13APR2022: Also flatten area circled in red.

Yup, they maximize every bit of space available.

This can also be addressed with stiffer engine mounts, which is why the STi mounts are recommended.

Good info but for me this issue was far worse. Not sure if I got lemon header or what but it still made contact in sharp left-handers even with with fresh STI mounts and a lot of hammering done to it. In provided example it's touching for me it was more like rubbing through :(
Now I'm about to install Beatrush under panel and hope for best.