insame1 is correct, SprintBooster will not make your Mercedes run faster.
While I cannot speak to its ability to add some excitement to a 320 (I have a 430), I wholeheartedly agree with Hary Gahtoe - it is a must upgrade. I was curious what all the fuss/debate was about with these things and found a cheap used one on ebay (about $150). My two take aways are 1) in hindsight, I would have payed full price knowing how it makes the car feel/drive; and 2) SprintBooster apparently has offerings which fit a variety of cars out there - I will never own another car, MB or otherwise, without one of these plugged in.
And yes, I do get how these work - I'm an electrical engineer and understand it quite well, actually. It's certainly is not adding or unveiling any previously unavailable performance, or any garbage like that (if you're looking for that or claiming that in your argument, look elsewhere). As the product states, it centers around increasing your car's throttle response - and the way it does this is fairly straightforward, from an EE's perspective that is. I thought it would be nominal or some junk you see on TV like any number of 'fuel saver' mechanisms, hence I opted to buy a used one knowing it wouldn't be a huge loss if my suspicions proved true.
Search through the boards for the 'internet dribble': You'll find one guy out of 20 that says he/she didn't like it/did noting for them, another 20 saying they were nay-sayers until they actually tried it, and a handful quoting the site who have never bothered to try it out.
If you want your car to feel like it has some more pep off the line and while driving, try this out. I didn't buy into the hype originally, but believe it is a great product and feel it is largely underrated (so long as nobody is arguing that it will increase horsepower, reshape the dyno, etc). Throttle response has a lot to do with how a car feels when driving. Beef that up with an above capable engine of an MB, and this thing is worth its weight in adding some fun to your ride.