If you’re looking for ultimate performance from a normally-aspirated VW motor, you may want to check out the Geers Engineering 51.5mm IDA carburettors, available through CB Performance.
Designed to maximise airflow and velocity, the units feature re-profiled throttle shafts, oversize (51.5mm) throttle plates and come with 44mm venturis and the third progression hole modification, which helps smooth the transition circuit from idle to main jets for street driving.
The Geers 51.5s also feature a modified float bowl for more fuel capacity and are supplied complete with CB Performance billet aluminium velocity stacks.
How much? $1,695.95 (+import duty, shipping etc. from the USA)