I had the "precat" too. I went to the muffler shop and ask the guy remove it but he said he will just clear it out, beucase i told him i think it was clogged. So he cleared it out and i noticed a big difference for a good 50 miles then my car started doing the same thing again.(when i hit the gas the engine hesitates to kick in, and horrible gas milage) so i dont know what else to do. I scanned for codes and the only one i got said something about the Egr valve.