It's all about emissions -- the premise being higher operating temperatures burn cleaner. If you're not squeemish, you could hard wire the cooling fan and add a toggle switch to control. But you'd have to cap the circuit that controlled the fan so that the ECU still thinks its there. There are a few options to do that, but do you really want to risk frying the computer?

I suspect (but haven't tried) that an option to hard-wire a cooling fan might be cobbled together out of those auxilliary laptop cooling fans. They're very thin so do facilitate some creative options.

For the truly brave of heart, has anyone ever done a shaker-type hood?