Only code is for p0136 and p0141 for Catless downpipe. The chain was supposed to be done before I bought at the dealer and have 0 rattle from it. Just the typical noisy lifters.
First thing I would do is replace the O ring on the BOV with the correct part. I agree with you that it's probably not the timing chain or you would definitely be hearing the "death rattle". Coil pack is still a possibility. If you have to put the car in service mode to check for that intake noise on the passenger side, while you're in there I would also replace the belt and if you still have the original plastic water pump, replace it with the newer metal version. You should check the crank pulley too while you're at it. I'm sure you've already thought of these things, but thought I'd throw them out there anyway.
It doesn't sound like the turbocharger, a bad turbo wouldn't work until it reaches higher pressures and then cut out, it would cause poor performance way before it reaches it's limits. I would look at the turbocharger bypass valve again. Do you have a boost/vacuum gauge? If not, you should get one to help diagnose this problem.
I do have a boost gauge. I hit normally I hit between 13 and 16lbs and then it does over boost occasionally to 21. But I'm starting to think it might not be boost break up. After driving around yesterday and trying to find it, it was more of a sputter for a second then it would continue to normal. So maybe something with the coils? Or maybe even a tune can fix it?
If you have aftermarket coil packs, they could be the cause of your problem. OEM coil packs are the best and can be used with higher horsepower mods.
The Engine Control Unit will cut boost if the boost pressure gets to about 23 psi. Maybe you are just touching that boost limit and the ECU is starting to cut boost.
So you're running a catless DP without a tune? My car (2007) does not like that. It will act very strange. Also, are you sure the repaired DP didn't fail again? I cracked once, its not as strong as it was when new.
