You most certainly want to lose back pressure, you have a turbo car + you shouldn't be worrying about scavenging effects. Get a 3.5" exhaust with good mufflers (e.g. Magnaflow), you won't have drone issues then. I run a 5Zigen 3.5" cat back (two mufflers), no drone at all and car went harder. Shame the mid muffler cracked and had to replace it with an inferior muffling Xforce one.
Popping and crackling is unburnt fuel in a hot exhaust. When is the last time you changed the spark plugs?