TAP

TAP stands for Timing Advance Processor.
It's installed to auto advance the frequency of spark.

By default, our car frequency of spark is 10 degree for petrol.
Anything lower will cause extreme underpower.
Anything higher will cause engine knocking.

Since NGV is difficult to burn compare to petrol, we need to increase the frequency.
The setting allowed is either 12 or 15 degree depending on individual car settings.

Once installed, the air restrictor/choker will not longer be required.
Reason being the choker method is classify as black magic.
Try telling mat salleh that we're using choker, they will respond saying "NO!"