So, I've replaced the MAP sensor, cleaned and used dielectric grease on the connector, used the updated MAP connector clip.

I've cleaned the MAP passage in the TB many times with carb cleaner.

I've cleaned out the IACV.

Symptom is stumbling from a start every once in a while, followed by a CEL later (not immediately).

What could be causing this? Only modification to the car is a K&N filter.

 

Check your Barometric Pressure (BARO) Sensor for loose vacuum hose and etc.

 

Wasn't able to find any vacuum leaks under the hood... Hmm.

 

Also, the BARO sensor is supposedly in the ECU according to the shop manual, but there are no vacuum lines going to it. Can't find it on the ECU. What gives?

 

Many resets later, still happening. Common locations for vacuum leaks?

 

Ok, so finally got around to trying a known good ECU. Same symptoms. New MAP, new TPS and good used ECU. The only thing it can be is a vacuum leak, right?

 

So, bumping this, should anyone else have the same issue in the future. Was down to a nearly-seized IACV. I removed the motor, and the barrel valve was very stiff and wouldn't rotate 360 degrees. I suspect it was sticking open and acting like a vacuum leak.

Cleaned it out, then it rotated smoothly. Reattached motor with new bolts, reset ECU and now it is fixed.

 

I like when people update when there is a fix. Thanks. Will help people in the future.

 

Thanks for the update ! Thats good to know and will help others