Elantra XD (2001-06) :: 2003 - Rough Start And Stalls On Full Tank

I just recently had a new (used) gas tank and new fuel lines (front to rear) put on the car.

On the first fill-up, I pulled out from the gas station, drove 20 seconds to the next red light. The car stalled (automatic transmission) when I came to a stop. It was hard to start and hard to keep going, and had intermittent periods of extreme power loss when I drove it down the highway.

Took it back to the shop, there was an engine code for the O2 Sensor, so the O2 was replaced, but made no difference. They checked fuel pressure and the catalytic converter, both were fine. They wanted me to keep driving it until another code came up.

As the tank neared empty, the car started driving almost perfectly. Filled it up again, and the problems started all over again. I have tried driving it with the gas cap off to make sure air can get in to replace the gas, but made no difference.

I changed the spark plugs, and all 4 of the old ones were covered in black carbon from the fuel running too rich (i assume).

Also, when the car is idling and it starts struggling, the exhaust does smell extremely strongly and is grey.

Now, engine code [P1166 O2S Controller Adaption Diagnosis Malfunction (bank 1)] is appearing (I have to check with the garage monday to see if it is the same code they had earlier).

I'm not sure why a new tank would cause this, unless somehow dirt/rust ended up where it didn't belong during the changeover.