Here's a tip... If no fault codes are present, then it isn't coil pack, injectors, fuel system and throttle pedal potentiometer related, they are monitored along with a plethora of other sensors. The MAF can show as no fault as long as it has signal but if you can rev freely, it eliminates that.
So that leaves spark plugs (which I doubt as no misfire is present in your description)Although oil spilt down the spark plug bores won't show up as a detected fault either.
Throttle body dirty, butterfly is trying to regulate but sticks on a fine ring of deposits so the idle sensor re-adjusts and the air to fuel mixture increases (probable)
Split or loose induction hose causing a an air leak which reduces the pressure measured after the MAF so a discrepancy between values (probable)
Breather valves and pipes causing The ICV to loose or increase pressure (unlikely but probable)
One or two other checks... What is your temperature gauge reading and how long does it take to warm up?
A faulty temperature sender switch that is offerng some resistance but on it's way out can also confuse the ECU into thinking the engine is warm when it isn't so tries to balance irregular sensor inputs despite being within values, so no fault shown (possible)
There you go