Proportioning valve leaks

Hey guys, I installed an aftermarket adjustable proportioning valve in my Dart, and one of the pipe fittings is leaking. I tightened it as much as possible, still leaks, they are brand new fittings. everything else on it is fine, its just the one pipe fitting. I thought maybe try some Teflon tape, but I feel like brake fluid would just eat through it eventually and leak again. Any suggestions?