If Mazda could get 3 or 4 hp, or even less horsepower loss as the engine heated up, and simplify the coolant plumbing process as well, why wouldn't they have done it at the factory ? Same goes for the grounding wire - if Mazda could improve throttle performance by strapping on $.50 worth of copper wiring, why wouldn't they have done it there ?
I can believe the grounding wire helps in certain older cars with bad electrical systems, but I find it hard to believe it would have ANY affect on a new car. Same for the coolant bypass - I just can't see why something so easy wouldn't have been done by the manufacturer if it had a positive impact...
Think about it - adding variable valve timing to the Miata in '01 gained them like 10 horsepower. And that's quite a bit of a change to the engine, just for 10 horsepower.
Based on threads like this, it seems like they could have just added a grounding wire and bypassed the throttle body with coolant to get the same 10hp...
I'm just a skeptic I guess...