I believe it's different for the 6 cylinder versus V8 so that will affect responses obviously. There are several older posts on this forum about changing the cats and in the case of the V8 the stock configuration has three catalytic converters - one for each cylinder bank and then after the last cat the exhaust becomes a single pipe and goes into a muffler before the tailpipe. There are complete cat assembly parts sold having all three pre-welded that I believe require you to loosen or remove a crossmember on underside of frame to fit. But I've heard other guys buying separate universal fit components piece it together as well. I usually try to tackle DIY stuff on the Explorer but this is one job I left to my local shop.