tippya5

Hey guys, so my 04 5.4 has seemd pretty sluggish lately and mpgs have gone down. I thought maybe a cat was plugged up so I looked into it. I took one of those infrared thermometers with the laser. 3 of the cats showed around 100 degrees increase after the cat. The fourth one showed about 30 degrees cooler. This one is one of the back ones so there are no o2 sensors for it. Does this sound plugged to you? Thanks

lewissa81

Get a back pressure tester. Like this one:
http://www.amazon.com/gp/aw/d/B0002S...I3RMITLMYJXXZ5