This twin V-Twin, twin turbo custom motorcycle debuted at Biketoberfest last fall and took Best in Class at the Rat's Hole Custom Bike Show. It was built by A1 Cycles of Wellington, Florida and is called "All In." The bike runs a 360 rear tire and a 310 front, not exactly a sportbike, but it's interesting nevertheless. The twin engines put out a reported 550 horsepower with one engine rotating in reverse.
Again, not exactly a sporty ride but they get a few points for the engine setup. V4s made from V-twins seem to be showing up more frequently. Is this a new custom trend? I think I prefer the AJS V4 myself.
Link: A1 Cycles
Another photo below: