My 2005 Tucson GLS 2.7L developed an intermittent hesitation problem late last fall. It occurs mostly (but not always) on cold days, from a full stop. It’s worse on inclines. I’ve taken it to the dealer 3X. The first time they told me a vacuum line had a split in it, they replaced it, and it was fine for a few weeks. The second time they said my air filter was filthy (it wasn’t), replaced it, and it was fine for another few weeks. This third time, they’ve decided it’s a fuel contaminant and they’ve recommended replacing the fuel filter, fuel pump, and fuel tank. I decided to pursue other options. I thought initially that it was a fuel issue, now I’m wondering it it’s an oxygen sensor problem. Any ideas?