So the Racechip seems different. I have only read what the website states and it seems to be more like an ECU tune but without flashing the ECU. My guess is it intercepts the stock tune, changes some parameters that then makes the car feel faster. Like a ECU tune but not as effective. My preferred method would still be a ECU tune from a reputable company like Eurocharged to bring the most out of my car. They do in fact "flash" the ECU and change the parameters but that would be maximum output as well as tailored to your vehicle/modificovations.

A device like the sprint booster or the one I posted is placed between the pedal and it's throttle sensor and will make your car more responsive by removing that lag that is felt in many European cars of that era. When you press the pedal there was that slight hesitation before the car goes. That's what these throttle input devices get rid of. If your BMW has that issue, this would still be a viable option.
You change the responsiveness according to taste....for example "stock"/"improved driving"/"race mode" all with 9 settings so you can fine tune how responsive you like it. A lot of time I have mine on 'improved driving" setting 7 and it feels great. But I also have an SRT and the Eurocharged Tune which did some help with throttle responsive as it is but I still don't wanna miss the throttle controller.
I set the controller to Stock the other day just to see the difference and when you are used to improved throttle response, it's a nightmare 😂
Keep in mind, these devices do not change horsepower, fuel mapping, spark times etc.