Some notes pulled from the Vortex 1.8T FAQ on maintenance/troubleshooting:
Symptom: Item to check
Rough Running At Idle: MAF, Ignition Coil, Spark Plug, VAC Leak, O2 Sensor, TB, CTS
Missfires under Boost Flashing CEL: Ignition Coils, Spark Plugs
Running Rich: Boost Leak, MAF, O2 Sensor, Coolant Temp Sensor
Running Lean: VAC Leak, MAF, O2 Sensor, Fuel Filter
Low Boost: Limp Mode, MBC, BOV, DV, Boost Leak, N75,
High Boost: MBC Setting, N75, Spark Plugs, Ignition Coils
Cold Start Problems: MAF, Spark Plugs, Fuel Pump Relay, CTS
Poor Gas Mileage: MAF, CTS, O2 Sensor, AIT Sensor
Cat Efficiency Below Threshold: Down pipe, CAT, Rear O2, RACE FUEL
No Start: Battery - ECU, Fuel Pump Relay, Ground
Start For 1 Second Stall: Immobilizer
Overheating: Waterpump, Thermostat, Head Gasket
oil in coolant: Oil Cooler, head Gasket, Water Wetter
Dies While Driving: Timing belt, Boost Leak, MISC
Shorts To ground CEL: Fuel Pump Relay, Bad Grounds
Oil in your IC/IC piping: Check your PCV system
If your synchros are grinding when you go to shift, a change in transmission fluid can help. For FWD's, Redline MT-90 is recommended and can be bought from ECS Tuning. For Quattros, there seems to be some uncertainty over whether Redline causes issues with the Haldex differential.
Haldex Fluid: The fluid in the Quattro's AWD unit (i.e. Haldex clutch) needs to be changed every 10,000 miles. Buying the wrench and fluid to do it is much cheaper than having it done.
Oil: use synthetic, else your engine could suffer from sludge buildup.
MAF: Cleaning the MAF with some MAF cleaner (get at auto parts store) can sometimes sort out issues with the engine.
Diverter Valve: If you have a Forge 007, lube it up with some fresh oil every oil change, else it'll wear out. For a stock valve, you don't need to.
Spark plugs: From the 1.8T FAQ:
OE Plugs: NGK PFR6Q - .032" gap
For Stock Cars - .032" gap:
* NGK BKR6E
* Autolite 3923
* Denso Iridium IK20
For Chiped Cars - .028" gap:
* NGK BKR7E
* Autolite 3922
* Denso Iridium IK22
**Avoid all non copper plugs, reommend to change every or every other oil change to keep from misfiring.
General Rule of thumb: For every additional 50HP over stock, a general rule is 1 heat range colder and gap shrinks by .004
--So, a chipped 1.8T would make good use ofa plug one range colder gapped to .028
>Tightening torque 30Nm (22 ft-lb)
>Tightening torque for Coil Packs 7ft lbs
I use BKR7E's. They're $9 for four of them off ECS Tuning. It's recommended to swap them every other oil change.