Problem with Tamiya paint

One other thing you can try is to put a drop or two of an Acrylic retarder in the paint after you mix and thin it. This will extend the drying time of the paint and prevent alot of tip dry on the Airbrush.(which could be what is causing your problem).
Tamiya paints are great for shooting through an Airbrush, but their dry time is so short. You can almost watch it dry in front of your eyes.

Paul

Is your AB needle OK, as in straight and all?

If your running a gravity feed AB you can run it 5-15 psi and lower the thinner to
around 5:2 or so

Definatly check tha paint to thinner ratio its always the problem when testing a new paint , for Tamiya acrylics I would suggest about 40% thinner with 60% paint between 10 and 20 PSI thats what I use normally when using Tamiya acrylics.

Thank you, I'll try that, the lines I have been noticing is a fine mist followed by a thick line as I make the next pass. the spotting problem I have corrected... the thinner was not at the correct ratio.

Not really sure what you mean by making lines or spotting......I've found that lowering the pressure a little prevents spitting......but I usually spray with a fairly heavily thinned paint - I hate the dreaded orange peel, you see.
Really, without a little more info, the best you can do is to run at that particular paint viscosity, try increasing and lowering the psi, and also the paint volume flow at each psi.
If you don't get very good results, try increasing or decreasing the amount of thinner you've put in the paint - it's a tough one, finding the correct balance - cuz every paint type is a little different.
Good luck!