This trick lasted for YEARS until Paypal killed it about a month ago. I never did this deal because my PPEMC was linked to my dead Paypal account, and I was too lazy to call and cancel and re-apply on my new Paypal account, which subsequently got the axe too. Eventually I gave up.
I don’t remember the play 100%, but it involved something like using your Paypal Business Debit card to earn 1% and you can specify your PPEMC as the backup funding source to earn an extra 2.5%. The main play here was that you could pay Citi using the PPBDC, so you’d earn 2% on the charge and 3.5% on the payment. Crazy double dip! Of course this no longer works since you can no longer specify your PPEMC as a backup funding source for your PPBDC. RIP.