John, where are you siting the meth in relation to the throttle body?
It is the pipe just before the throttle body. The pipe is a very soft 90 degree pipe and has a different diameter inlet to outlet and is really too soft to support the injector without loads of internal and external washers and nuts. This is the pipe that I'm having modified to have a custom stainless pipe section, specifically to hold the injector. It will have a flat section welded onto it and and be drilled through and tapped with a BSP thread so that the injector has no internal nuts or screws holding it in place that could come loose and get sucked into the manifold. I've heard that this is not the ideal location from one other source due to the remote possibility of the throttle valve getting damaged over time, but this was by using impure methanol and the location is the best point for maximum benefit from cooling and power. Approximately 8-10" from the valve itself.
Oh and here is a quick photo of the rear install. The pump is gravity fed from the bottle and so has to have it's intake point below the bottle bottom. Luckily on the Polo the boot section is very deep and allows for this. Full credit to Statllers as they made a really neat job of the install and pipework.