Originally Posted by SeeeeeYa

"Thermal mass" is the reason. In daily driving that thermal mass does just that... absorbs a large mass of thermal energy. That heat, largely from the engine, is both larger and lasts longer in the HEAVY aftermarket TMICs.

The single most significant power-related "benefit" of most aftermarket TMICs is the fact they have less internal resistance. That, to me anyway, signals a loss in efficiency as well.

Not to mention raising your center of gravity with a ton of aluminum up high.

I've done both. Read the NASIOC thread.