Is complex.
There is the dopamine itself.
Then there is the receptor-- D1, D2, D3, D4, D5
Then there is binding affinity
Then there is the dopamine transporter

People vary at birth and during development based on genetic heritage on the ratio of neurotransmitters in the brain. There are two basic types of people.
1) high arousal types --prone to anxiety and with more serotonin actions
2) low arousal types-- prone to risk taking, drug use, etc to raise the dopamine hit reforcement cycle.

Some forms of depression are thought to be affected by dopamine.
When dopamine gets "low" prolactin typically goes UP. And you state your levels are normal.

So what I think is that you might be mildly depressed. Because you are relatively young, this is a mild depression. With time and age you may see this increase with more striking symptoms.

When you take tyrosine, you are increasing dopamine in the body, and also the synthesis of epinephrine. The epi is what gives the tightness in the chest and other unpleasant symptoms.

I think your options are to 1) lower your tyrosine dose so you don't get the chest tightness, 2) seek an opinion from a psychiatrist as to whether you are depressed or not. Typically to improve dopamine functions in the brain, the drug Wellbutrin (Bupropion) is used.

Another route you could try is SAMe. This natural substance that our bodies make increases neurotransmitter synthesis in the brain.
Young people typically start at 200mg in the morning on an empty stomach and don't need high doses.

I found an interesting list of what is in mucuna:
http://sun.ars-grin.gov:8080/npgspub...xsql?taxon=644
Notice that it is high in arginine. This amino acid improves erections in men.
It also stimulates viral replication, and if you have herpes it can activate it.

Since you are concentrating better also on the tyrosine, I'd consider ADD for you. There are interventions that improve concentration without drugs.
One is to take Essential fatty acids, Omega-3s.
Along with magnesium supplement and B6.
This is my magnesium thread:
http://neurotalk.psychcentral.com/thread1138.html

And this is the EFA thread:
http://neurotalk.psychcentral.com/thread6092.html
The EFAs work by making the membranes of the brain cells more flexible, and hence the
receptor site more efficient in accepting the neurotransmitter molecule.

So I think if you are serious about your issues, a visit to a psychiatrist may
be useful for you. Minor depression also resolves with SAMe and EFAs, for many people. So you may not need stronger drugs.

The problem with mucuna is that both India and China have problems with purity. Tainted herbs are coming out of both countries, and the problem is growing and not getting better. So it is rather risky to use an herbal product these days.

If your search Dr. Sahelian, he has monographs on many nutrients. I'd check him out before trying anything new.

Good luck, and be careful!