[asphaltgambler]

Yes, there have been carb spacers around since the late 60's originally pioneered by S&S. With long duration cams on hot street / drag engines the turbulance in the manifold is high. Some so severe at mid-RPM's it causes carb stand-off which is where the atomized fuel is pushed out backwards past the venturi.

Unfortunately, there is only so much length that can be added due to space / location limitations. One way is actually lengthen the area outside venturiusing a longer velocity stack ( hot street/ drags application ).

Testing has been done using a 90 degree curved intake placing the carb / throat inline with the travel of the bike. The reasoning is twofold: you lengthen the intake manifold considerably isolating the carb from all the turbulence and increasing the ram effect of forced air into the carb with the bike at speed.

BUT - in reality it never works, makes less power because the large volume of air has to make a sharp 90 degree turn slowing velocity down and heating it up. Plus the forced in coming air creates more turbulence at the outside of the venturi.

Modern aftermarket fuel injection systems (S&S again) have just about solved this as now the fuel is delivered directly behind the intake valve allowing the manifold and throttle body to be sized exactly for air flow only. The space / locations still exist though.

Also, big power today in modern; read aftermarket HD engines are now square ( bore / stroke ) to just slightly under square with very high flowing, efficient designs. This creates less turbulence in the intake tract