The work shop manual lists the following as possible causes:
-Misfire
-HO2S (front) deterioration
-HO2S (front) heater malfunction
-PRC solonoid valve malfucntion
-Pressure regulator malfunction
-Fuel pump malfunction
-Fuel filter clogged or restricted
-Fuel leakage on fuel line from fuel delivery pipe and fuel pump
-Fuel return hose clogged
-Leakage from exhaust system
-Purge solonoid valve malfunction
-Purge solonoid hoses improper connection
-Innsufficient compression

Then, under the "Diagnostic Procedure", step 8 is to check MAF signal and step 9 is to inspect for excessive air suction of intake-air system.

I would take a gander and say to check you intake installation and make sure your connections are tight and your MAF is installed correctly. It could be causeing the MIL indicator to light up from not being recalibrated to your intake yet.

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Nik Jaremka
2001 Black Mica Protégé ES