Need help using AP datalogs to identify an intake/exhaust leak...


New member
Hey guys, I tried posting this on VWVortex, got a ton of views and not a single reply, seemed pretty quiet over there so I figured I'd try here since my account has FINALLY been verified and I can officially post and no longer just be a lurker!

Hey guys- new to the forum and looking for some help! First of all, my car is a 2014 VW GTI, 2.0T (CBFA if it matters) with DSG, with just over 53k miles that I bought back in February. Within less than a week of owning the car, I got my first CEL code for the intake manifold flap issues, stopped by my local VW dealer, who diagnosed it and offered the replace the intake manifold right there on the spot under warranty. About a week after that repair, and after a little spirited driving one night, another CEL code for a underboost condition fault. Again, stopped back at the VW dealer who diagnosed it as a bad turbo, and again, offered to replace it on the spot for free under warranty, along with new DV, etc. Inconvenient, but ultimately I decided it was all actually best case scenario because now with car has a new turbo and the intake manifold replaced at just 50k miles. Over the past few months, I've since upgraded to a Magnaflow cat-back exhaust (sounds awesome), then added an aFe complete cold air intake (stage 2 style) which added a little more fun factor. Had an issue with the first intake, had a bad grommet which caused it to leak oil from the pcv hose connector at times, so a call to aFe later and they shipped me a whole second free intake, new pipe and grommet, which has since sealed much better (seemingly perfectly as no oil leaks ever now.

Now more recently I've bought a Cobb accessport for it, and set it up with their 93OCT stage 1+ tune, which it ran really well with (at least it seemed) but wanted to tune it more specifically for my particular mods, and decided to turn to Stratified Tuning and got a flash tune from them. After a few days I received my flash tune, a 93OCT single tune, with their free MAF calibration. After flashing the tune to the car (which made an AMAZING difference in power and overall performance), and putting over 40+ miles on the car, I followed their datalog instructions and made the two specific runs, and emailed the .csv files back to them. A short time later, one of their tuners emailed me back and said that based on my datalog files, it appears I have an intake/exhaust leak, and to correct the issue first, and their suggestion was to take the car to a shop to smoke test it to identify the leak. I emailed them back asking for more specific information, like what parameters in my datalog files led them to that conclusion to help me in diagnosing my leak, but have yet to hear back from them yet, so I was hoping some of you much more turbo tuning savy guys could maybe take a look at my logs and tell me what seems out of order. I am by no means new to cars, this is probably somewhere around my 30+ something vehicle (I'm 28) however it's actually my first turbo car, so I'm still trying to learn all I can there. I believe what may be of red flags might be my AFR's, because I notice that while monitoring the gauges on the AP, sometimes, when I let off the gas and coast, sometimes the AFR's read 235.05 until I step on it again. At idle, in drive, they're typically around 14.41-14.95, with an occasional blip over 15.10 or so. WOT usually sees somewhere around 10.85+/-, sometimes only low 11.XX's. Also, my boost pressure always reads lowest 0.0, occasionally -0.2 max, and up to a max of 23.1 but usually no more than 22.3 +/-, and I don't know how accurate this really is. I also find the 0.0 reading off because I know in my gf's 17 wrx, her factory boost gauge reads negative boost pressure (vacuum I assume) when at idle or very low rpms, whereas my boost pressure seems to never go lower than -0.2 max, and I don't know if that normal or not. Anyways, so far that's all I've noticed. I'll attach my 2 .csv datalog files and if anyone has the time to review them and report any issues they find, I would appreciate it greatly!

Also for what it's worth, the only occasional issues I've noticed is when trying to accelerate slowly, sometimes I get a little surging in boost, which can make it a little uncomfortable for passengers as it feels almost like I'm quickly goosing the throttle momentarily, when really I'm just applying normal smooth throttle pressure, which I assume to be associated with this leak issue.

Thanks again!


P.S.- A recent update; last night Stratified responded to my email, and said quote "From the logs, it looks like the LTFT and STFT are a little off"... That only confuses me further, because according to Stratified's instructions, all FT's must be between .85-1.15, and throughout the entirety of both logs, as well as every other mile I've put on the car since while monitoring, my FT's have never once stepped outside that range, even by .1. So to conclude, according to Stratifieds instructions, my AFR's are within spec, my Knock is within spec, and my LT/STFT's are within range, so I am kinda scratching my head as to what is leading to the claim I have a leak, and how to address finding it. For what it's worth, I did mention all this to Stratified, but like my last response took 6 days, I'm still waiting on a reply.