I run the factory-stock ITBs in my four cylinder E30 M3. BMW Motorsport homologated them on this car so that they could race them in various series requiring "stock" motor parts. There is no problem with fuel economy or whatever with ITBs. If an ITB car has crummy gas mileage it's for other reasons.

ITBs can allow a bit more torque and HP and noticeably increase throttle response. ITBs plus throttle position sensor and possibly MAP sensing = ultimate throttle response. Feels very crisp, easy throttle blips for downshifts etc.

Stan

 

The extra air is only added if you ask for it (Throttle Pedal). Generally though, if you have access to that extra power (air), then you're gonna use it. If you use it, then you're gonna get burn more fuel.

 

It's odd that BMW would add the ITB's and then tack on drive by wire which completely erases their gains in the throttle response department.

 

That's what I thought, also, but if you think about it... BMW has the Sport button. My guess is that because they have drive-by-wire, they can soften the throttle response for "normal" driving, and then kick it back up to 100% instantaneous (as though it were a mechanical throttle cable) for "Sport" driving. That's the only reason I can think of why BMW would use drive-by-wire on their M cars. I compare it to Honda's VTEC - two different levels of performance, Dr. Jekyll and Mr. Hyde, if you will.