What Big J is saying is partly correct. You're not really going to "gain" any velocity by running it back but you're not going to suffer the loss of velocity down the pipe by not having it there. Too many people run too big of an exhaust and it does affect horsepower. On turbo engines its not as severe as an NA motor but its still there. If you run the dump far enough down the DP, at least 12-14" or more and merge it at as shallow of an angle as possible you can lose the "fart" sound as you call it without any real loss in power. In 99.9% of turbo setups though you will always make more power with a divorced wastegate setup but you have to deal with the noise. As for it running on 3 cylinders, it doesn't really work that way unless you have a twin scroll manifold which in that case your manifold will have a better designed wastegate supply. The turbo sees so much flow/pressure, if you bleed off from pretty much anywhere in the system it will work the same with minimal differences. It sounds like you need to plumb the dump back in as the noise seems more important than the few HP you'll lose in doing so.