Another P0299 thread

Hey guys I have a 2006 GTI and just 2 weeks ago I went to APR Stage 2+. For a few days I've been feeling the car underpowered and yesterday the car threw the P0299 Code and waiting code of misfire on cylinder 3. So I checked everywhere but no one else had the waiting code of cylinder misfire, is there anything I should be looking for specifically? I was on 93 octane program and switched to Stock right after that. I checked everywhere but could not find anything broke or disconnected. Could it be the Diverter Valve? I changed it 4 months ago and is a Pierburg, I got from ECS. Any help would be greatly appreciated.

Thanks, that info is very helpful.

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Update, the Diverter Valve I replaced in May got stock on the down position and that was my issue. So just because you have a new part and is the right version of it don't assume its not the issue. $169 later I learned my lesson.

I have the p0299 code as well. Car was running sluggish. Replaced DV. still has problem and a high pitched noise like air escaping or something? I have climbed under the car to check for leaks, but cant hear anything. Any ideas out there?

2006 Volkswagen GTI (1K1) L4-2.0L Turbo (BPY)

I have P0299, P0300, P0301, and P0303
car start up smooth and runs smooth. but any time i got up in the high rpms it bogs down and misfires a lot to where the engine shakes.
just installed:
new timing belt kit installed
new spark plugs
new updated Diverter valve
new updated CrankCase Pressure Regulator Valve w/ turbo breather hose and seals
new OEM coolant (pink/violet)
when driving the exhaust sounds kinda like it's backfiring.
when parked and reeving the engine and letting off it still sounds like it's backfiring.
no cracked hoses. no loose connections etc...

all coil packs have spark when testing. changed spark plugs because the old ones...well they looked old. timing belt replaced based on mileage. OEM diverter valve replaced because the seal inside was worn. replaced with updated diverter valve. crankcase pressure regulator valve seal was old and worn out, so it was replaced with a updated one with the recommended updated breather hose.

starting to think i have a bad/clogged catalytic converter... just need a second opinion.

i know a Catalytic converter, when going bad/ clogged it can cause a cylinder misfire and/or multiple misfires.
and when looking around on identifix, i looked up P0299 and misfire codes and Catalytic converter, DV, and CPRV seem to be a common fix.

May be a fueling issue http://www.audizine.com/forum/showt...ost-DTC-No-boost-leak-foud-What-to-check-next