Re: bypass valve for CAI (ioiwin)
you should never use a bypass on our cars..carbonio says so
Can I fit a bypass valve to the Carbonio system?
Any device that is placed in the inlet stream compromises intake performance. For those customers, however, who are willing to sacrifice some performance for peace of mind, commercially available bypass valves do fit the Carbonio system. Please note below, however, that bypass valves may be unsuitable for certain applications
The bypass valves that are currently available are designed to operate under longitudinal loads (i.e. forwards and backwards along the axis of the valve's centreline). If these valves are installed improperly, in such a way that they operate under lateral (i.e. side to side) loads, they can break prematurely, and in some cases, cause broken bits of the valve to enter the inlet tract. As more Carbonio systems are introduced, we will indicate the suitability of bypass valves on a case-by-case basis.
The MK4 VW
The engine compartment in the MK4 VW leaves no room for the installation of a bypass valve, except on the portion of pipe that lies immediately after the Mass Air Flow (MAF) sensor. A bypass valve does fit here, but results in the valve operating under lateral loads rather than the longitudinal loads for which the valve was designed. As a result we recommend that you do not install a bypass valve on any MK4 VW.
you should never use a bypass on our cars..carbonio says so

Can I fit a bypass valve to the Carbonio system?
Any device that is placed in the inlet stream compromises intake performance. For those customers, however, who are willing to sacrifice some performance for peace of mind, commercially available bypass valves do fit the Carbonio system. Please note below, however, that bypass valves may be unsuitable for certain applications
The bypass valves that are currently available are designed to operate under longitudinal loads (i.e. forwards and backwards along the axis of the valve's centreline). If these valves are installed improperly, in such a way that they operate under lateral (i.e. side to side) loads, they can break prematurely, and in some cases, cause broken bits of the valve to enter the inlet tract. As more Carbonio systems are introduced, we will indicate the suitability of bypass valves on a case-by-case basis.
The MK4 VW
The engine compartment in the MK4 VW leaves no room for the installation of a bypass valve, except on the portion of pipe that lies immediately after the Mass Air Flow (MAF) sensor. A bypass valve does fit here, but results in the valve operating under lateral loads rather than the longitudinal loads for which the valve was designed. As a result we recommend that you do not install a bypass valve on any MK4 VW.