VAG help -> misfire-like issue

[S4evr]

so im still having this engine problem, let me explain. (car is AWE stage 3 with old, non-mbc file BTW)

roughly 2 weeks ago i stepped on the throttle and once i got up 15lbs it felt like i hit fuel cut/throttle cut, something like this. i've never had it happen before. thinking it was a spark issue and my plugs were VERY old, i changed the plugs. i changed them, went out for a drive and the problem seemed to go away. a day later i am merging on the highway and step on. in 3rd gear i notice the problem returning just slightly. just a little bit of mis-firing above 15lbs. i didnt think anything of it and then when i shifted into 4th and got up to 15lbs, the problem really hit hard. cel popped up and started to flash at me. i immediatly let off the throttle and 2-3 seconds later the cel stopped flashing, but stayed lit. i had a very funny burning smell during those 2-3 seconds as well. not only did it sound like it was missfiring, i could feel a vibration coming from the rear of the car.. very weird. since then i did a few non VAG related tests as i dont have VAG right now. the problem is definetly greater with a higher load on the engine. (22 lbs in 2nd has less issues than 22lbs in 3rd, and so forth) i havent pushed it hard enough to get another flashing cel yet.
my friend is coming tomorrow with VAG. i've never used it, and he hasnt used it for diagnostic purposes either. what should we log, how should we log? car on/off? driving? idling? full throttle? what should we look for?

[RolledMySTi]

First just check for codes before you log. You can have stored codes with no cel. If you have misfires in most if not all cylinders you most likely have a boost leak. Have you pressure tested? If you have a misfire in just one cylinder try swapping coil packs to see if the misfire follows.

[S4evr]

just pulled the codes, heres what i got:

16815 - Warm Up Catalyst: Bank 2: Efficiency Below Threshold

P0431 - 35-00 - -

16805 - Warm Up Catalyst: Bank 1: Efficiency Below Threshold

P0421 - 35-00 - -

18014 - Rough Road/Engine Torque Signal from ABS: Electrical Malfunction

P1606 - 35-00 - -

18010 - Power Supply Terminal 30: Voltage too Low

P1602 - 35-10 - - - Intermittent

16684 - Random/Multiple Cylinder Misfire Detected

P0300 - 35-00 - -

16688 - Cylinder 4 Misfire Detected

P0304 - 35-00 - -

[MissingPixels]

Sounds like a boost leak to me. Pressure test and post your results.

As far as your codes go, I would suspect an O2 sensor (probably two) for the P0421/0431. I'm sot sure about the P1606, but I wouldn't worry about it too much at the moment - clear it and see if it comes back... What type of transmission do you have by the way? The P1602 is from disconnecting your battery and the misfire codes could be a result of your boost leak.

Again, I would test for boost leaks, then clear your codes and let us know if any of them come back.

[S4evr]

cleared the codes, ill see what happens. is there a way to pressure test even tho i dont have an air compressor?

[highPSI-S4]

Did you resolve the issue?

I'm having the same issue with my car but i haven't had time to pressure test it yet.
Just looking for an update.

[Evilevo]

The P0431 and P0421 are from having DPs with HighFlow cats. Dont worry about them.

[S4evr]

i havent had time to try to fix anything. CEL came back about 10 miles later after i cleared the codes, but i havent had time to re-scan it to see what came back. once i get my hands on a vag again (not until november 15th) im gonna try switching the coil packs around to see if the misfire follows.

If i am sitting in the driver seat, like i am driving. what is the cylinder # layout?

[S4evr]

could a dieing fuel pump cause this? i mean, i have almost 105,000 miles on the car and its been stage 3 for atleast 15,000 miles so a worn out pump could be the cuprit. what you guys think? any way to test the pump?