Legitimate electric blowers do exist however you are looking at at least a $2000 investment. A legitimate electric blower system will have its own battery or disconnect the battery from the cars electrical system while in use so as not to bog down the engine with the alternator. As far as economy goes though I have my doubts. This might pay if you had a diesel (as boost can increase efficiency in a diesel) in pure stop and go traffic with very long red lights but its unlikely.
The piper must be paid and using an electric blower you are taking out a loan so interest must be paid too. You borrow energy from the battery to create the boost, then you have to pay it back with the power sapped from the alternator. A direct drive blower or a turbo are more efficient as you do not have to pay the alternator efficiency tax.
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