I worked on it this weekend. The cat was defineately causing excessive backpressure. Just for 'test' purposes I enlarged the flow path to 1.25 inches(3.3cm). After reinstalling the header pipe with the precats and the main cat, I took it for a short spirited drive in the country to blow out any debris that might remain( and there was some). It felt like it had more power and response but I didn't drive far enough to measure fuel consumption. I will install the muffler system and check that later this week. One thing I did notice though, it requires about 250 -300 rpm less to maintain 60 miles per hour.