I was interested to see that members are still carrying out the airbox mod. I thought some who have done it might like an update. I originally developed and implemented the change in October, 2003 and it's still going strong, 12 years later, without any problems. I've replaced the duct tape about every three years on the Fresh-air duct (snorkel) to ensure that the system remains airtight but, other than periodic OEM paper air filter replacements, no other upkeep has been required.
In August, 2007, I installed a Racing Beat Cat-back exhaust system which further enhanced performance by reducing some restriction at the other end as well. I highly recommend this addition to those who have already carried out the airbox mod as the best way to obtain a moderate increase in volumetric efficiency and reduce pumping losses without actually having to go inside the engine. According to Racing Beat's chassis dyno data, their cat-back system produces +4.7 HP @ 5750 rpm and +5 lbs./ft. torque @ 3800 rpm. The BHP ratings would, of course, be even higher.
Finally, I've carried out some intake air temperature studies by using an Outside Air Temperature gauge with its sending unit mounted in the airbox. Very briefly, I've seen airbox temperatures climb to as high as 140* F after prolonged idle or stop-and-go driving situations, but during constant driving at normal road speeds the airbox temperature remains at just a few degrees above the ambient. Since cooler air is more dense and therefore BHP varies inversely with the intake air temperature, this is further confirmation that an SRI would seem to be a poor choice for an intake.