Thanks for the help guys, cut out the cat and replaced it with a straight pipe and the problem is fixed.

I have one more issue that bothers me. My truck seems to shift into overdrive too quickly. If I hold the accelerator it will take off fine, but be in overdrive by the time I reach 35 mph. I also notice when I use cruise control and hit the resume button the rpms will drop down to 1200 and take a long time to get up to 55 mph. I can override this by pushing the accelerator down further, but was just wondering if anyone knew what would cause this. The tps was changed about 5000 miles ago.