Eb2 to EB3 downgrade ( I140 with prev employer)

[mchepuri]

• EB2-I140 approved with priority date May 9 2013 with EMPLOYER1
• Switch employer to EMPLOYER2 in Sep 2015
• Have been getting visa extensions on previous approved I140.
• No PERM started with EMPLOYER2.

Can i downgrade my Eb2 to Eb3 that is with my previous employer ( assuming previous employer is willing to help)?
If yes do i need to go through labor and I140 again?