^^^ THIS would be good to verify to at least rule it out; there was a firmware update to some of these PCMs to rectify a mis-calculated alcohol level. If you're not running E85 or anything over E15, the alcohol value should track the actual within a few percentage points and be below 15%.
Post up your MAF reading in g/sec at hot idle. It should be very close to the engine displacement in liters.
Post up the short- and long-term fuel trims, both banks. Does the fuel system go into closed loop?
You can test for vacuum leaks by using unlit propane around your intake tube as well as any vacuum lines or the intake itself.
If the fuel trims are very positive and have been for a while, there may be fuel contamination in the oil, and the trims are going to struggle to right themselves without changing the oil. But that's a bit of an WAG without having more info.
You could have bad O2 sensors or a leaky injector, etc., but without some of these data it's going to be challenging to pinpoint it.
