[billymade]

If there is oil, in the spark plug wells; this has a grounding effect, can cause misfires and eventually wipe out the coil packs. Pull the plugs, spray out the oil residue; from the spark plug wells and the bottoms of the coil packs (be sure to stick with genuine vw or oem replacement coil packs; not the typical aftermarket ones, you get from typical auto parts stores). Vacuum leaks, can cause misfires as well; the evap diaphragm, located in the valve cover, is another common failure. This can cause a large unregulated vacuum leak; replacement of the whole valve cover or a repair kit; would be a fix for that, Dorman or RKXTech, make affordable repair kits.

re: 2.5L PCV valve failure solutions from Dorman!

re: 2.5L PCV valve failure solutions from Dorman! The 2.5L; has a common issue, where the PCV valve fails. Up until now the only option; was to buy a whole new valve cover from Volkswagen (VW doesn't sell the PCV separately); at $225 or more, plus install... it is a pretty expensive fix with...

www.newbeetle.org

When removing the valve cover; it is also, common to find split vacuum hoses/pipe, going to the brake booster, which will cause another vacuum leak. Inspect that for damage/splitting; you can wrap with electrical tape and a worn gear clamp; as a temporary repair but replacement, is recommended for safety reasons (vacuum to the brake booster).

Note the possible reasons; for the trouble codes, listed here:

16684/P0300/000768 - Ross-Tech Wiki

wiki.ross-tech.com

For the spark plugs, stick with oem brands; NGK, is typically the oem for VW.

Beyond that, you might check your fuel trims (+ or - 10%: is considered normal range) and then, @ almost 160k, test the fuel pump and see, if it is weak or failing.

Fuel Trim Info - Ross-Tech Wiki

wiki.ross-tech.com

Keep posting any trouble codes you get; this can help, diagnose the problem (misfires, other vacuum leak codes, etc).

Let us know, what your troubleshooting and repairs reveal, we can discuss more, as things move forward, we can go from there.

 

[billymade]

16555/P0171/000369 - Ross-Tech Wiki

wiki.ross-tech.com

The vacuum leak, from the brake booster; typically, will cause a rough idle and misfires. I don't know, which scan tool you have but I would be looking at live data, confirm, what the fuel trims are. Because, of so many changes, have been done; it may take a bit of driving to get everything relearned but you could try a hard reset of the ecu, then all the settings would be cleared. I don't know, if the brake booster hose; is perfectly sealed but replacing that, is definitely recommended from a safety perspective, you could still have a vacuum leak there.

Fuel Trim Info - Ross-Tech Wiki

wiki.ross-tech.com

You might confirm your fitment; i came up with this:

Brake Vacuum Hose

Part Number: 7P0611932AN

7P0611932AN - Brake Vacuum Hose - Genuine Volkswagen Part

Genuine Volkswagen Part # 7P0611932AN (7P0-611-932-AN, 7P0611932AF) - Brake Vacuum Hose. Fits Touareg

parts.vw.com

Many times, there is a difference; if there is a automatic or standard trans, confirm with your VIN #. Cheaper oem versions, can sometimes; be found from vendors online, like RM EUROPEAN, AutoHaus Arizona and FCPEURO, etc.

 

[billymade]

So, I would keep a eye on your fuel trims; + or - 10% being considered, in the normal range. If after the brake booster hose replacement; you still have fuel trims out of spec, I would start checking things on the list of the ross tech definition. Older VW's, tend to have weak fuel pumps; so, checking fuel pressure and confirming it is in spec, would be one of the common failures.


16555/P0171/000369 - Fuel Trim; Bank 1: System Too Lean
Possible Causes

• Mass Air Flow Sensor (G70) defective
• Intake System Leak(s)

Possible Solutions

• Check Mass Air Flow Sensor (G70)
• Check Fuel Pressure Regulation
• Check Fuel Pump
• Check Injectors
• Check Intake System for Leaks
• Check Exhaust System for Leaks
• Check Secondary Air System for Leaks
• Check Vacuum Pipes for Leaks

Drive the car, keep an eye on fuel trims, maf sensor readings, any trouble codes and report back, we can go from there.

 

[billymade]

Good work; glad you got it fixed!