Yes air still come through the vent. A bit in the back is open so not as much but it is functional.
The price...it was $30 plus shipping the the Roush pod, the guage was something like $65 shipped from Prosport. I bought a hot glue gun and glue sticks for about $7 and the rest was all fabrication. I used hacksaw blades, files, adn sandpaper from my job. Pretty easy install with the walk through I read on the forum here. I'm not one at all for taking apart my cars interior but I thought it was very easy. I'd say if 1 was easy and 10 hard it was like a 3.