Can anyone tell me how to tell if my cats are starting to plug up? i seem to be down on power alittle but not bad yet. im starting to smell my cats more then before. is there a test i can do?

 

you still have the stock cats?
Rear O2 sensors?

 

yes stock cats, rear o2 turned off use one of them holes for wideband thats realy acting crazy

 

with my old setup (flow master delta flow 50 single 3'' in, and dual out 2.5'', and stock cats 145k miles on them muffler around 60k. I rant a 16.6ish with the 20s) then resently i was getting at most 325 miles per tank.

new setup (magnaflow big body single 3'' in single out 3'' out, magnaflow high flow cats, asp pulley set. I ran a 15.4 in the 1/4 with the 20s... ) well my milage came back to a better high around 430 miles on a tank... I do plan on throwing some new sensors when I get some headers...