It appears that you are looking for a second opinion. Please seek a private consultation with an experienced immigration attorney in NYC to accomplish it.
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Impossible to give a meaningful answer without knowing all the facts, I.e. examining the new PERM position; comparing to the old; and etc. Spend a fistful of dollars to sit down with a local immigration lawyer to examine in detail and tell you.
Behar Intl. Counsel 619.234.5962 Kindly be advised that the answer above is only general in nature cannot be construed as legal advice, given that not enough facts are known. It is your responsibility to retain a lawyer to analyze the facts specific to your particular situation in order to give you specific advice. Specific answers will require cognizance of all pertinent facts about your case. Any answers offered on Avvo are of a general nature only, and are not meant to create an attorney-client relationship.
PD retention is generally do-able unless the first I-140 was withdrawn. The "upgrade" that you refer to in the second part of your question is possible sometimes but very case-specific. An attorney would have to closely review the PERM job requirements, among other aspects, to determine whether this it is a possibility under your circumstances and advise your employer accordingly.
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I agree with my colleagues, from the description it is difficult to understand your current strategy. If you could port, it is hard to understand why you would do a new PERM.
The above is intended only as general information, and does not constitute legal advice. You must speak with an attorney to discuss your individual case.