The ecu uses the MAF(RL) reading vs and a constant of around 0.082XXXX to work out the (RK) relative fuel which is then worked out in to (TE) injecton on time. When the car is under part throttle, light load and idle the ecu run at lambda 1.001 for emmission control. With the maf in place the mapping of the RL RK with give the correct injection on time to achive lambda 1.001 this is called open loop fuel capped by closed loop fuel trims. With the car running spot on the injection on time should be around 2.04ms with the block 32 fuel trims at 0. So if you have a 16mm hole in the tip the RL reading will be incorrect and the fuel trims will be all over the place to correct the closed loop lambda control.
When the car has fault code in will run lambda of around 0.93 which is richer,again with the RL via maf the trims should be 0. When you disconnect the maf the fuel will run in a generic TE based on a ecu calibration and closed loop lambda, the problem is fuel trim if they are over -/+25 on both add and mult then the car cannot fuel correct and will run rich which on idle and light load will wash the cat out and produce a really bad smell.
So that the technical part sorted. Now for the low tech part of my post.... A bit of chopped off wooden broom handle will fit in the 16mm hole sweet as a nut..lol
