Might need a bit of DRIVING with injector cleaner in the (93 octane) gas!

I will let someone more knowledgeable and experienced tell you WHAT cleaner to buy, but I DO use SHell or BP gas almost all the time. I think this will clear up in time, IF it's a dirty injector problem. And I really think that is what is going on here. (Again, not a mechanic, but I hang around with one a lot.)