Cats on 5.7 OBS 2500

[majbutch]

OK, trying to read all I can but need help.

2000 OBS (1998 style) CrewCab 4WD 5.7 - has two cats with O2 Sensors before and after on both if I am not mistaken. Approaching 150K miles and feel I may need to do something with cats. What to do? I am currently running a dual in/out Flowmaster 70 series. No emission test in Alabama. Fuel mileage stinks so I am open for suggestions.

Muffler shop said 2500's had larger cats and they usually don't see them clogging as often and they generally flowed well even on OBS. ???

Thanks.

[DylanC]

Tune out the o2 sensors and cut the cats but with a 2500 your not going to see any better mpg that's a heavy truck what's your gear ratio?

[majbutch]

3.73 Gears

[1988 GMC 355]

Changing your o2's is more important than getting rid of the cats.