If you permanently disable the sensor (ie disconnect it and replace with a resistor that always reads "cold") the ECU will eventually find the fault and you'll get a cell. the ECU has strategies: ex. on cold start coolant temp and IAT can be compared...on a cold engine they should be about the same...if there is a big deviation it will set a code and possibly go to an emergency map = low timing and dump fuel with the goal of preventing knock. These cars have electronic throttle, the ECU if it detects a big enough "problem" may limit throttle opening (limp mode). Otherwise it can check for open circuit (disconnected sensor) short circuit (resistance too low) and sometimes simply a lack of sensor change over time will set a code. Even if the ECU thinks the sensor is ok if you over-advance timing you'll hit the knock sensors which will pull out lots of timing and/or dump fuel to control detonation...resulting in reduced power output.

If you wish to try this (I don't recommend it) I'd suggest a circuit that on startup allows normal sensor output, then switch in a resistor to change resistance to a colder temp indication once the car is in closed-loop mode, then turn it off prior to shut-down. And change your oil often if you run excessively rich...you'll get fuel in the oil.

A better strategy would be to log the stock IAT, compare it to ambient temp, and find a way to make it cooler/stay closer to ambient (ie CAI, shielding, etc.).