L-TYR is definitely water soluble; NALT is "more fat soluble" according to one study I found, which implies that L-TYR is perhaps slightly fat-soluble.
But my understanding is that, even with h2o+fat soluble amino acids (ALCAR is also one), they're fine to take on an empty stomach because of the water solubility, and are absorbed better because of the competition problem kilgore mentioned.
I would definitely take L-TYR on an empty stomach.
No tolerance. Ive been using tyrosine in the am on an empty stomach for probably 20 years. Works wonders. Dont really feel down without it... but definitely feel "even better" with it, still, every time. Give the machinery the raw materials, and it cranks out the neurotransmitters without fail... and they do their thing without fail every time forever it would seem. I think thats an important part of how the brain is built. Probably because neurotranmitters are involved, not stimulatory drugs. Thats where the caffeine, etc. come in!
I'm not saying I doubt your experience, but based on my understanding I find this really hard to believe. The problem with increasing amounts of dopamine by any means, whether it's adderall or tyrosine, is that the brain won't accept higher levels of NTs forever. There is downregulation on the receiving end, which means that if more is produced, the brain will compensate by deploying fewer receptors. It might be worse with stimulants because of the additional mechanisms and greater magnitude, but it's still the same principle.
A lot of people on the forum have mentioned that they develop a tolerance pretty quickly, like in the space of a week. Do you ever take breaks to see what the effect is?