Could one of you kind folk shed a little light here for me?...

…why do the Testors MM enamel whites spray so crappy? Ive even switched over to the gloss! it like spits all over.
Would turning up the air pressure help?

I usually spray everything at about 18-20psi.

It almost sounds like a thinning problem. I’ve never really had a problem airbrushing any of MMs lighter colors including white but I do add a little more thinner than I add with the darker colors. When you add extra thinner you mignt consider dropping your air pressure a little. You’ll probably have to do some experimenting to find what works best for you.