I have walked once over a K&N on a gas engine. It let enough extra air AND DIRT by that it built up a 1/16" layer of dirt on the idle air control valve. The valve would do a touch so the ECM would know where it was and the 'touch' kept the dirt off the area it touched only. I learned this after it started and stalled over and over. It would rev up, but, couldn't be put in gear as it would not idle. Fixed itself at the dealer and NPF. Later I watched the tach as it was idling at 450 RPM when it was supposed to be 600 RPM.
The ECM was using a table to set the idle air control. The 1/16" of dirt was reducing the airflow, running rich, and stalling the engine at too low of an RPM to run.
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all throttle bodys get dirty regardless of filter used