In Nov I purchased flyingfish Tial 605 Pearl Avant. This weird thing happened on my first pull leaving his house to drive cross country. Car starts to make boost then burbles and looses power and wont build boost, it gets between 5-10psi and then boom the burble/mini backfire and then no power. it drives fine idles fine and most of the time it pulls hard with no issue. A handful of times the car will be pulling hard at high RPM and the car will have a abrupt cut in power, like you pulled the plug. This issue comes and goes and I always have 0 codes thrown from it. I have found in my testing that with the aquamist off it still has the promlem without the small backfires. One other thing I noticed is that when its having this issues you don't fell the boost even build up at all before it does it. The boost gauge reads boost between 5-10 but you don't feel it. When its running good I can feel the boost build and start to pull.
Fast FWD to Today first time I have driven it in two weeks. Drive to work and it runs amazing with 0 issues, text the old owner and say I think I finally fixed it. I was pumped..... Well on the way home boom same issues. I hate how it just comes and goes with no real rime or reason why it decides to act up.
I have replaced over the last 4 months in order.
bypassed N-249 valve
new 710N DVs
updated to FSI coilpacks deleted ICMs
checked for boost leaks, found some small vacuum leaks replaced a few lines
coolant temp sensor
New aquamist HFS-4 controller to replace HFS-3
Old owner did EGT's and O2's within 5-10k miles
Any ideas from you guys would be great.. Do you think I could have a bad ECU? Not sure what else there is to replace, especially when I don't get any codes at all.