i just got my converters replaced 3 years ago for $1600 now my check engine light is on and i went to my mechanic and he said they needed to be replaced again i see converters on jcwhitney.com for $130 can i use these? or are they different? what sensors do i have to put on them to make them work? please help i feel liuke im bein ripped off here what tools would i need to replace them to?(btw if u cant already tell im new here) also what is a heater box? can i take it off my system and still be legal?