So, replaced the cat, still high on CO. Decided to clean injectors. Found the injectors that were in the truck were rated at 208cc/min as opposed to the stock flow of 195cc/min. The stock ECU can compensate for 8-10% and the 208s are @13% too big. Installed a set of stockers balanced at 188cc/min and we'll see how that goes. Might just change the O2 sensor for S&G.