The V&H system looks very nice! Here's what I heard back from Klock Werks:
1) Yes, the short SS Slash Back is a 4” muffler.
2) Although no muffler on the market is guaranteed blue proof, there is no reason to worry. We have never—even after extensive dyno runs and tuning—experienced any bluing on our pipes. Our baffle thickness and chrome plating is top notch and there are few other mufflers that can even compare. Obviously, negligence and carelessness while tuning could cause any brand of muffler to blue. Just make sure you dyno chief is top notch and problems will be nonexistent.
3) The fuel management system we have used and continue to recommend for the 2010 models is the Dynojet Power Commander with an Auto Tuner. These work the best, and we receive the best results while using them. For the older models, (older than 2010) we prefer Zippers Thunder Max.
4) Our decibel numbers (keep in mind all numbers vary when different meters, locations, and operators come into play) are very comparable to V&H. However, keep in mind that decibel numbers are usually subjective.
5) While revving up the bike, our mufflers will probably have a little more bark, and while at a cruising speed they have a lower hum. Our customers did not believe us until they went for a road trip and had full conversations with their passengers!! These pipes are remarkable!
Although our 2010 Double Back Header Systems are not available yet, they will be soon.