Airbrush nightmare

As someone who used to paint cars in another life, this looks more like a surface prep problem than a paint problem. Make sure the surface is absolutely clean and rough it up just a bit with some 600 grit sandpaper.

When the paint is dry, make sure to pull the masking tape off properly.

The RIGHT WAY - pull the tape back on itself.

The WRONG WAY - pull the tape straight up off the surface.

I am certainly no expert when it comes to painting models, but I hope this helps.

In addition to the above, I will add (based on your image) that you painted the yellow over the blue.

If possible, paint the yellow first (after surface prep again) and mask for the darker color, blue in this case.

Usually, you should try to paint from light to dark.

Next, it looks like the yellow is/has "orange peeled" meaning the yellow paint did not go on completely wet. The paint has already started drying from the time it left your airbrush to the time it landed on the surface of the engine. Try painting at a lower PSI or slower passes or thinner paint.

Get yourself some plastic scrap and some masking tape and practice different combinations of the above settings and see what happens.

Hope this helps.

Charlie

Rich is right on the money with the surface prep.

I still use the Tamiya paints with no problems .   I get mine off EBay or Amazon.    I haven't used the Model Master paints .  I'm sure there are different quality paints that forum members use.

When I paint directly on plastic parts I use Zippo lighter fluid to wipe the area . Zippo leaves no residue and doesn't melt the surface of plastic .   Plastic contains oils and when the surface is wiped with the Zippo it sort of frees that area of the oily chemicals.

I actually use Acetone when prepping the surface for gluing only ( not painting ) since  it will begin melting plastic. 😨

Thanks for the good tips.  Shell was originally dark blue.   I didn't paint yellow over blue.  I did prime the entire shell white, then masked off the area to be yellow and painted the blue.  Then masked the blue and painted the yellow.  The tape pulled off both the paint and primer.  I gave the shell a very light scuffing with 1000 grit as I didn't want to lose any detail.  You can still see the two "V" stripes under the yellow.   I'm using an old Paasche brush with air reduced to 20psi out of a 5gal pancake compressor. .  It did seem that the consistency kept changing as I sprayed and would sometimes be down to nothing but air coming out.  Had to keep readjusting. 

I must also hang my head low (very low) for my tape peeling technique.  I never thought there would be a right and wrong way to peel.

I would agree that it is surface prep, as the paint peeled off of some but stayed on the other, plus, it took the primer with it.
I would add that when you peel back the tape on itself (as Rich has shown), do it at a 45° angle away from the line of paint.

So, this is not an "airbrush" problem at all.