I bought one vent for $11 and made both vents for the liners. I cut the vent in half and then trimmed to 3/4" from the vent openings to remove the flange and excess metal. Then I bent the vents by hand to match the curve of the liner. Drilled 1/8" holes around the edges a couple inches apart. Then started drilling the liner and installing aluminum rivets from the back side so the head of the rivet supported the soft plastic. I could have installed them from the vent side but I didn't feel like driving to buy the backing washers. Once painted and installed it's nice. On the TT fwd fenderwell liner under the intercoolers there's a venturi that vents the exhaust side of the i/c. The larger i/c's sit higher and lower in the opening so they interfere with the venturi positioning the lower part of the liner down almost 2". So I mod'd them flat like you see with the same .025 aluminum sheet that I made the ducts out of.
