Alright, I've done a BUNCH of Google'ing and forum searching, and as soon as I think I have found an answer, I find out it's not MY situation due to one reason or another (like it's an FSI problem). So I pre-apologize to those who know where everything is and hate my search skills. I bolded my questions in the event that you want to skip through the diatribe that follows.
In one fell swoop, I had the following installed:
After leaving the garage the first time, it wasn't long before I got a CEL (P0420), likely due to the Hi-Flo 200 cell cat in the EJ TBE. This was cleared up by installing an O2 sensor spacer. They had also forgot to replace the stock DV spring, so my boost was limited to 12psi (bleh) until they replaced it (now: 22 peak, ~18 sustain until the engine runs out of RP range).
- Eurojet Gen2 VBand TBE
- Forge Diverter Valve
- Forge Twintake
- Forge Catch Can
- APR Stage 2 Tune
After leaving the garage the second time: when I got home (45 minutes from garage), I ran the Torque App engine code retrieval and saw a pending P0507 - RPMs Higher Than Expected and a P0101 Mass Air Flow. Now most of the drive was highway, but I did notice when getting off the highway that RPMs hung up ~1500, did a hunt-and-search down and back from 1200, before finally dropping to normal (~750). I cleared the code, but it has come back on every drive since.
I took the car back to the garage, and the mechanic explained to me that by removing the PCV, during the catch can install, I effectively removed the vacuum check valve (CV) in the stock unit, as the "Africa plate" does not have a built-in CV. He called the resulting configuration an "open system", whereas the stock system is "closed". By having an open system, he continued to explain, the blow by gases enter the intake after the MAF, and the difference between the MAF reading and the turbo intake reading causes the computer to trip the P0101. He additionally "proved" his point by removing the oil cap (which would normal cause the car to run rough or outright stall) and the RPMs remained unchanged.
Question 1a: Is it the intent of a Catch Can design to create an open vacuum system? Is that how it performs its function of collecting the vapors?
Question 1b: If the answer to the above is yes, does that have an effect on the performance of the car (increased crankcase pressure / blow by gases in Intake)?
I've seen posts talk about this on MKVs, but with regard to the FSI, where replacing the Crankcase Breather Valve hose with one that has a built-in check valve, would resolve the P0507/RPM issue. This does not appear to be a solution for the TSI motors.
Before someone suggests scrapping the CC and returning to stock PCV, the mechanic found that my PCV was failing when he replaced it.
Question 2: Would adding a CV (somewhere before or after the crankcase) eliminate the P0507/RPM issue while preserving the functionality of the catch can?
I got interrupted here and my train of thought derailed... if I can provide any more information to appeal to the diagnostic Gods, please let me know and I'll get it. I have the Torque App and can run some checks, but I'm not an expert so you'll have to instruct me a little.
Thanks in advance for any and all help. The car is a monster right now, but I don't want to reduce the life of the engine/drivetrain if there is an underlying issue as indicated by the CEL codes.