OK...the shop replaced the fuel pump. I assume they drained and cleaned out the fuel tank also...that is good. I have seen moisture/water in the gas..do many stange things to a engine...

You say is drives Ok...but surges during idle now and then? (not all the time?) How about high speed, with a constant speed say 60mph....any surging ??

I also assume it is showing NO codes ??? Did the shop say everything is fine???