I guess you already saw an ENT about the issue?
What kind of ETD do you have? Clogged tubes? In that case, regular (and careful)
nasal irrigation might help.
There's
one study about diving-related medical disorders (divers seem to suffer ETD and inflamation of the tubes quite often), which, among many other things, mentions ETD.
Unfortunately the study is not available for free on the internet (at least I could not find a public version), but here's the interesting part about ETD:
Also, one of the authors has an
informative (but German) page about ETD.
It basically states the same as above: Carefully try to do the
Valsalva maneuver 50x a day to train the muscles asociated with the tube and do
nasal irrigation at least twice daily.
However, be extra sure that you don't have Patulous Eustachian Tube, or everything might get worse.
Also, be extra careful while doing this stuff, don't use too much force.
If that doesn't help either, there's - at least in Germany, don't know about the US - a rather new therapy where they insert a small balloon-like thingy into your tube and inflate it.