[Wolfman77]

Yeah tachyons are all technobabble, but how does exhaust make sense? What exhaust does a matter-antimatter reaction produce? The only thing I can find is that they produce gamma-rays (funny how that ties in, huh SJ?). We can detect gamma-rays wit hour current level of technology, It's only fair to assume they can as well. Therefore cloaking devices must block any gamma-rays that the warp core shielding doesn't, or they would be spoted quite easily.

Since we are keeping the artificial gravity, masking that signature should be doable.

I suppose we could say a few gamma rays leak through, compareable to background radiation, but if their sensors are configure to look for only to wavelength produced by certain engines, they could at least narrow it down. Especially it the source is moving. Still a bit of technobabble, but no tachyons.