Lowend

iTrader: (5)

My 2004 STI has thrown codes twice in the last couple of days. I'd like some opinions

This car has Top Feed Conversion with 1000 Injector Dynamics. It also has the Delicious Tuning Flex Fuel conversion.

Both times the code has been P0172

#1 was Saturday, driving on the freeway. CEL and Cruise light came one. I pulled over, did a visual check, found nothing. When I pulled codes on the Accessport, P0172 was listed as "Fuel System Bank 1". I reset the ECM and everything was good for 2 days. I put ~ 80 miles on the car without reoccurrence. I did notice a little stumble in the 3000RPM range occasionally. The car was on 91 Octane at the time. After this, I threw in a tank of Shell 91 Octane just to make sure it wasn't bad gas.

#2 was tonight (Tuesday) driving home. Code P0172 again this time with "System too Rich (extreme fuel trim)" I had filled half tank of E85 earlier in the day
This time I had the presence of mind to grab a memory snapshot before I reset the ECM (attached file)

Doing visual inspection, I did notice a hum coming from under the engine compartment I hadn't noticed before. Took a video to capture the sound
Key was on, I tuned off the HVAC. This could be normal, I've just never noticed it before.

Overbear

Almost sounds like the fuel pressure regulator is having issues, that it is letting the pressure fluctuate up and down. That would be my best "educated" guess.

The buzzing sounds like the throttle body actuator, perhaps it is going bad? Who did your tune you may want to run it past them, there may be something in the data that can point to what is going on past the code.

Lowend

iTrader: (5)

Mann hooked it up to their smoke machine and vacuum was tight as a drum

We cleaned the MAF and everything cleared right up.