I have the Gemtech suppressed bolt carrier and I LOVE it.....I bet I get a 70-80% reduction in gas blowback in my face. However, with you being a lefty, all that gas is going to shoot straight into your face, unless you shoot right handed. Maybe check out a suppressed charging handle. B.A.D. levers are great too, but if you shoot left handed....again, same thing. I'm a righty, but have ambi controls on all my rifles.
Unfortunately, have to shoot long guns left handed, even though I'm a righty. Only have one good eye and it's on my off-handed side.