Custom cold air intake

Gday
Just thought I'd throw this one out there. I'm sure it's been discussed at length before but has anyone managed to make their own cold air intake. I've got an EF falcon 5.0 and I've done a few mods to the engine (heads and inlet manifold plus exhaust) but I'm still using the stock air box and cold air intake with just a K&N filter. Is there really much gain in getting a bigger cold air intake and can you just make one?
Cheers
Mark
Just thought I'd throw this one out there. I'm sure it's been discussed at length before but has anyone managed to make their own cold air intake. I've got an EF falcon 5.0 and I've done a few mods to the engine (heads and inlet manifold plus exhaust) but I'm still using the stock air box and cold air intake with just a K&N filter. Is there really much gain in getting a bigger cold air intake and can you just make one?
Cheers
Mark