I asked the same guy about my 3.4 and he said he would have to know what injectors I was running in the 4.3 TBI. He also said I would have to convert to a 3 wire O2 sensor. He had concerns that the 02 in the x-pipe on mine was too far back when it is actually closer forward than the Cat conv. was. He also said it would be $120.00 instead of $80.00.