2001 hyundai sante fe v6 4wd

[jsteezy1290]

i have 01 sante fe awd v6, i have no cel light on but the i took it to the dealership and they told me one of the manifold converters melted down and clogged something up which is restricting air flow and resulting in the truck having no power and i picked the car up from the dealership after they gave me a 2800 quote to fix and took it to the 3 muffler shops the first one said nothing was clogged and they didnt know what it was, the second said there was no way to really test it besides trial and error and the third said they couldnt test it properly with anything because theres converters in the manifolds so they can test it with pressure, so i then took it to a transmission shop to make sure that wasnt the problem and they confirmed by saying its not. please help i need my truck back and its almost impossible to drive espically if i have to go up a hill..