when NOT to use "beaucoup"

[alan gould]

"beaucoup" is my logical choice instead of "plein de" in the 2 following sentences and yet I've seen examples like them before.  I'm sure I would not be wrong to use "bc" and yet "plein de" is used even though it would seem to translate as "I am full of..."   (google translates it as "I have plenty of...")   

J’ai plein de cadeaux à acheter 

J'ai plein de trucs à faire demain.    I've got loads of things to do tomorrow. 

I would choose "bc" instead of "très" in the sentence below but apparently it can modify a noun and be translated as "very much" 

j’ai très envie d’y aller 

If there are other examples of this, please share.  thank you.  

[George Hunt]

J'ai très faim,soif, peur, honte

 

http://www.google.co.uk/search?num=100&hl=en&safe=off&c....

it seems to be limited to  that kind of a usage.

I don't feel it is modifying the noun rather  the  verbal construction as a whole(as an alternative/synonym  to "bien" perhaps -unless it is just an error in syntax that  has become current in the language as an idiom)

[Neil Coffey]

Some prescriptivists have considered "très" to be an "error" (but remember that when a prescriptivist says "this is an error because of such-and-such syntax-based reason" what they're really saying is "my syntactic model is too weak to account for this data" or "I have decided not to like this and am trying to convince you that you for some reason must adopt my opinion").

However, it's been common for at least 100 years or so. In more formal usage, you can indeed use "bien" instead.

[alan gould]

actually, I've never heard "j'ai bien [faim, etc.]"  only "beaucoup" is logical to me but apparently i can expect to hear "bien" as well.