The Citgo name change message has been making the rounds since 2006. It's not new.
I don't know if the Snopes.com information is still up to date, but it notes that Petro Express is privately owned by The Pantry, Inc., which is headquartered in Sanford, North Carolina, and not owned by Citgo or the Venezuela government. It also notes that Petro Express outlets did once sell Citgo gasoline but the company stated in October 2006 that the chain would be phasing out sales of that brand by 2007 and that shortly after Pantry, Inc bought the company it stated that gasoline sales at Petro Express would be converted to Chevron's Texaco brand.
This may or may not apply in the case of Citgo:
People get e-mails from unknown sources and then want to boycott the wrong companies? And boycotting the correct company may not accomplish the goal anyway. Go figure.