[Sid Squid]

Some unburnt fuel will always pass through the engine, a race exhaust won't make any difference to that. A pop in the exhaust is caused by that fuel igniting, a leak in the header will do this, or in the case of many modern bikes including a Pointy SV, (which you may have but you don't say so it's hard to know if this is the case), there is a system called PAIR which introduces oxygen rich air into the exhaust under certain circumstances, to encourage that fuel to burn as an emissions reducing measure. This is the popping and banging heard from the exhaust of many a Pointy, and plenty of Curvys that have a less than perfect seal at the front header sleeve joint. Even with a standard exhaust this happens, but the silencing makes it harder to hear, if I listen very carefully to my SV1000 on standard cans it can just be detected.