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1) A has / had found B which I feel / felt is very lucky

2) A has / had found B which I feel / felt was very lucky

Can anyone advise me on this two sentenses & explain how & when to use them?

(as in when to use present/past tense in this sentense)
Comments  
I'd say

A has found B, which I feel is very fortunate!

Notice the comma after B. This is a non restrictive clause. The adjective should describe the situation (A has found B). I wouldn't describe a situation 'lucky'. I'd use the word 'fortunate'.
If your B is a person, you may use 'lucky'. But I would lose 'I feel'.

Ali has found Bill, who is very lucky.
Thank you lagataw for your reply. Can you please also advise me on the three sentenses below. Which is right & which is wrong & when to use them.

1) A had found B, which i felt was very fortunate!

2) A had found B, which I feel is very fortunate!

3) A has found B, which i felt was very fortunate!
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Sorry. I just came back home from a three-day vacation.

All three are correct depending on the states of affairs.
You must remember, though, that the past perfect (had + Vpp) is used with past actions or events that happened before a past time (expression) or another past action.
The tense of relative clauses (here) is not really influenced by the tense of the main clause so you can use "I feel...is" and "I felt...was" depending on whether you still feel it is fortunate. You may even use "I feel...was" if that's really how you feel.
uthebleachi1) A had found B, which i felt was very fortunate!
uthebleachi2) A had found B, which I feel is very fortunate!
Before the bandits came (to kidnap Belle), Aaron had found her, which I felt/feel was very fortunate. ( for me feel ...was is the best combination here...because until now I still feel that it was fortunate)
uthebleachi3) A has found B, which i felt was very fortunate!
On second thought, this one doesn't sound good. So not all three are correct.
A present event/action cannot have an effect in the past (unless it is in the conditional case e.g. If I were Superman, I would have been able to save the little girl.)

-Lagataw