Cold Air blockoff  - description, pseudo FAQ
Have you ever noticed that your first WOT of the day feels real fast, then after that the car feels slower?  If so, this is the mod for you. 

I started with a 3 foot by 2 foot roll of roofing insulation material from OSH (that is the silver stuff), and a 2 foot by 2 foot sheet of cardboard.  Total supply costs: $3
I then removed the air filter, and cut the cardboard out as a template.  I cut the cardboard so that it would go all the way under the fusebox until it met the frame, and even cut a notch so it would seal against the air filter bracket.  The concept here is to make sure there is nowhere that hot engine air can get to the air filter area.  In this picture you can see where the blockoff passes under the fusebox. 
This picture shows how the blockoff seals the filter area off from the top.  I didn't do this with my last blockoff, and I as a result it was ineffective. 
Sealing off here is easier than trying to seal against the hood, which I have seen with other blockoffs. 
Once the cardboard template was complete, I cut out two sheets of the roof insulation material based on the cardboard template.  I then glued it to either side of the cardboard (i used spray-on glue, but anything will work here, even staples). 
If i were to do this again, I would use some more heavy duty insulation material, but it is so effective like this, I haven't bothered. 

You can see the cold air duct which I am running from the front bumper of the car.  This is critical, as when you are sitting at stoplights a little hot air can manage to get past the blockoff (I guess the blockoff "heat soaks"

I will post some more detailed pics tomorrow, to show in more detail what the template ended up looking like.  All in all this took about 2 hours from start to finish, but that included throwing away two templates because they didn't come out right.  This mod was cheap, quick, and effective.  My butt-dyno says every pull is just as powerful as the first.  Extended highway blasts backed this up.  This is much more effective than my last blockoff, which was just a sheet of metal (see left). 

old blockoff
Blockoff Sandwich
Cold air duct