The CEL typically indicates a fault that will result in increased emmisions due to the engine not running as efficiently as the computer thinks it should. The mods you mentioned are harmless and shouldn't cause any problems, unless one of the hoses or electrical connectors around the intake area is loose/disconnected. To further diagnose, you really need the fault code from the computer. (Dealer or garage, or a friendly Autozone) My Firehawks lasted about 35K miles.
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