If you don't mind V4 mode, you might as well leave it alone. I purchased my tahoe with 200k miles and AFM was enabled. However, the lugging in V4 mode bugged me. I only want the range device if they get a carb eo number.
Which ever way you tune it out, should not affect your idle (If you notice the truck always idles in V8 mode) There are many devices that use the OBD port all the time, and I haven't heard of any reason for that to be problematic. (other than a device that drains too much power and you not driving for long periods of time)