2000 blazer LS approx 80k Starts great idles good . Around town drives fine, shifts, etc.
Take it on hwy , punch it...bogs down. Sometimes tech races forward, without shifting. Settles at 60m.The odd time it works perfectly....low end torque etc. Was throwing a p154 / p155. Changed oxygen sender pre cat. P155 went away. Thinking maybe Cat Converter. Also have fuel gauge issue, have not done fuel pressure test. Any suggested direction would be appreciated.

 

Eliminate plugged cat by removing the pre-cat O2 sensor and going for a drive. Will need to put some kind of deflector to keep the hot exhaust from hitting the floor pan; wedge a piece of sheet metal in somehow. This will set of course set the P155 code again. If the bog down is gone, then cat is plugged and next step will be to determine why; rich fuel mixture; before replacing the cats.

If cat replacement is required, recommend obtaining the Y pipe with both cats instead of just cutting-out the main and installing a universal main cat. The pre-cat is not available as a separate unit and is also likely clogged-up.