I have heard that increasing the bore of the throttle body improves low end power and/or response. Is that true for all cars, or only cars whose breathing has been improved to the point that the throttle body becomes the main restriction?

What is the trade-off? (I know this sounds cynical, but rarely do you get something for nothing.)

 

Changing the intake, throttle body, intake manifold, and exhaust components will alter the power characteristics of the car. By changing the throttle body alone, you can actually lose performance...a restrictive intake coupled with a very non restrictive (higher volume) throttle body will increase air turbulance and cause air to enter in gulps instead of a smooth flow. Of course a slightly larger throttle body would probably be a good thing in all scenarios, but too large may invite unwanted results. Civic and Integra tuners are probably the best people to ask since they have an easy and cheap access into the realm of aftermarket parts. Maxima owners on the other hand take the advice from a guru tuner and experiment with OEM parts from other cars

ie, Pathfinder Throttle body
5th gen muffler
Middle Eastern intake manifold

I would suggest the Pathfinder throttle body and possibly polishing or port matching it. Anything larger may actually be bad. On another note, I've heard of throttle body spacers that a lot of 4X4's use. They can increase the low-end response and power, yet will sacrifice the top end...but when you're off-roading or towing, you have no business redlining (unless your stuck in the sand or ditch).