Hello CAFCNA!!!! I'm back again with another code to chase down. P1400-00 This one popped up a couple days of no issues, no CEL. Chasing other codes several days prior, I replaced the Throttle Position Sensor, Mass Air Flow Sensor, and Air Filter. The throttle body seemed to be in pretty good shape. No built-up dirt or anything. It opened and closed easily with no issues or restrictions. The CEL....P1400-00 just popped up after about a good 2 days of no CEL. Also, there's no noticeable performance issues or symptoms. From what I've learned so far, there's a couple thing(s) I know to check but don't know how to actually do it. That's check for exhaust leaks and vacuum leaks. What are the necessary tools, techniques and procedures? What else could be causing P1400-00 to pop up? Thanks to everyone!!!