I would agree with doog - I never, ever use straight Future (as a gloss coat), and rarely use clear coats at all, flat or gloss.
The only time you actually need to use an overcoat is to protect dry transfers from oil weathering, as they are very fragile - especially the dark colors.
It's always annoying when something turns glossy, but there's an easy fix that won't damage the pigments too much.
Mix 1 part Tamiya flat base with 5 parts Future floor polish, then thin that mix 50/50 with isopropyl alcohol (so it's thin enough to airbrush, otherwise it will splatter)
This will give you a thin, ultra-flat acrylic clear coat, that doesn't yellow with age, isn't thick and yucky like every lacquer clear coat is, and won't affect the pigments as much as lacquer (although very subtle effects will still probably disappear)
You MUST test this mix before applying it to your model (as you should with any clear coat). If there is too much Tamiya Flat Base in the mix, it will turn white and chalky, and if there's too much Future, it will turn glossy and darken the finish.
The Tamiya Flat Base has no pigment in it - it's simply a mixture that dries so flat it looks white. If you do get too much flat base in the mix and it turns white on your model, just hit it again with a properly mixed overcoat and the white will go away.
The really nice part about doing flat coats this way is that you can control the exact sheen by adding more Flat Base or more Future.
Once again, while this technique uses Future, it's not anywhere near the same sort of thing as using straight Future. I would agree with doog about that being less than ideal, and know from experience that gloss coats are totally uneccesary if you use decal setting solutions properly.