BRZ EcuTek Throttle Stumble

Hey guys - I'm tuning my BRZ with a Perrin cold air intake and unequal length headers.

My fuel trims while driving are pretty good, +- 4% under most conditions without even making any adjustments to the stock calibration so I believe my MAF scaling is good.

But, when taking off from a stop in first gear, or giving the car a light tap of 30-40% throttle at idle, it has a heavy stumble and lag before the revs come up.

In my logs, the short term fuel trims go about +20% momentarily when you first tap the throttle. I've tried adjusting my MAF scaling in this area (15-60g/s) with no change. I've added 20% here to the MAF scaling and it doesn't get any better.

Can anyone help me out here? I can happily post logs, I'm super lost. Thank you!!

Posting logs if anyone has time to take a look and point me in the right direction.

Are your only hardware changes the intake and headers? If so you should fine the engine runs almost perfectly on the stock ROM. What changes have you made from stock to the ROM? At this point I've tuned multiple 86's with both N/A and FI engines and none have required any changes to aspects around transient enrichment which is what it sounds like you're having issues with so it makes me a little suspicious that something else is going on.

Thanks for the reply Andre!

Actually, I should have clarified, the car is a 2014 with a 2017 Model engine and hardware installed. The only hardware changes to the engine from stock otherwise are the headers and intake. I'm running the OEM 2014MY ZA1JB01C ROM with currently no changes to it. I tried making some fuel trim changes around that MAF scaling zone but made no change to the stumble condition.

1. did you check if there is differences in the two stock roms(14 to 17)

2. did you look here http://www.ft86club.com/forums

3. Why did you change to unequal length headers. I have noticed on the WRX cars, when switching from OEM unequal length headers to equal length headers. The fueling changes for the better.

4. How long was the 2017 engine sitting on a floor. Did you clean the injectors?

Are you aware of the mechanical issues for the old cars.

i.e failing fuel filter, di seals cam issues.