how do you know if your catalytic converter is clogged?

low power, small exhaust flow, etc

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-Alex
'10 Ranger XL 2.3L Manual
Mods: Stereo, Tint, Weatherguard rain shields, Intake silencer removal, LED brake, turn signal, reverse, license plate, and dome lights, DDM HID's (currently removed), lowered, 17" wheels with spacers, Explorer autodim mirror with Autolamps, Magnaflow exhaust, Buggman LED 3rd Brake Light...

you will feel the loss of power for sure maybe a rattle like broken parts shuffling around inside of a metal case.. just like S13minus1 stated low exhaust flow and maybe if its bad enough a check engine light set off by the 02 sensor

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2009 ford ranger Sport 4.0L V6/2 8" red hot glasspacks swept side before rear tire/2 catco high flow cats/K&N 77 series intake system/BFG all terrain 31x10.5x15 tires/Procomp 98 series rock crawler black rims/westin black sportsman brush guard/6-6'' Hella 500FF lights/black rhinoliner/Bilstein 5100 shocks/uniden 68LTW CB radio/Fx4 skid plates/cranked Tbars/autometer vaccum, Camper shell with thule roof rack/ belltech shackles/Pioneer headunit with pioneer speakers with Kicker 10'' sub

yep, ive got that sound going on too...guess i should have scrolled down before i posted my thread...

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2002 Ford Ranger with 142k
31in Cooper Discover ATR
Gibson 2.5in Cat back exhaust
CTC Camper shell
K&N Panel filter

It could also cause you to get bad gas milage...