I used the stiff boost line for mine, it's been fine. According to their online instruction manuals now, boost fittings don't have the tee anymore, they use a compression fitting which is probably why you didn't get one... If you'd rather use the fitting you got with the gauge, you could drill and tap into the intercooler near the cold side instead. If you haven't got a tap, an engineering shop should be able to do it fairly cheaply I'd imagine...
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