I'd have to disagree that the use of a cone filter doesn't provide power/torque gains.
I added a KKM kit with the S&B cone filter and aluminum MAF adapter, with no other new mods, and there was a very noticeable increase in power and torque.
The use of generic cone filters and generic adapters won't give the same result though, since those filters are just for cosmetic purposes, the stuff they're made from isn't made to flow air really well, and the adapters don't match up to the same size inner diameter as the stock MAF assembly and so it just creates turbulence rather than increasing airflow.
As for CARB certification, you won't find CARB certified intakes for vehicles like the 91-94 Explorer as they were already last-generation stuff when cone filters and intakes became popular mods. Certain vehicles like 90's compact cars were the exception since they were super popular to modify, being they were also inexpensive to buy and operate.
You also won't get a CARB certification since the use of a cone filter results in the loss of the vacuum system for the airbox and the heater hose on the stock air duct. This is the case on most other vehicles as well, but for the Explorer with it's big OHV V6 and earlier OBD I programming, the loss of these systems results in a lot of extra emissions on startup and until the engine and catalytic converter warms up.
If you want a cheap and easy mod that will pass inspection, just get a K&N, S&B, or Fram AirHog stock replacement air filter. It will flow more, and is really all you need with stock exhaust. If you want even more airflow, you could also drill some holes or cut a big hole in the fender side of the airbox - or even cut a hole in the sheet metal and make a custom cold air intake by connecting the inner fendewell to the air box. Whether or not it would pass inspection would depend on what the laws are at the time where you are located. Sometimes anything before the air filter is ok, sometimes anything at all that isn't factory won't pass and you'll have to go somewhere else.
