In most homologated exhaust systems there is a restriction at the manifold connection which meets the cylinder, the GP4 exhaust from Tecnigas is different.
The GP4 has been restricted on the exit of the system, the hole is very small and gives a similar effect to the normal restriction. You could call it an alloy spacer, washer or bush, regardless of name it needs to come out if you want to get beyond 30mph.
The crudest way and by far the quickest is to simply insert a bar or even a screwdriver with almost the same diameter into the washer hole making sure when you push it in you don't make contact with the baffle tube. WD40 would be useful making it easier to work the washer out using a rotational movement.
Once out the system will be free from restrictions enabling an increase in top speed making your journey that bit safer. The sound tone will also change, we think it's more in line with what you would expect a 4 stroke to sound like.