Unfortunately, from
my testing warm air intakes do not effect warm up hardly at all. I'm sure they don't hurt, but its not a noticable difference. You'd be better off blocking your grill off and/or insulating the engine. I'm in a similar situation right now with a 7 mile (11km) commute and I will be insulating my engine soon, adding a block heater and I also have a full grill block.