Probable causes of pinking on a digi GTI? Solutions?

[cняis]

Problem:
What might be causing this? it was set-up as per "the guide" about 12 months ago, although it was running a "higherpeaks" style replacement ECU chip at this stage. I removed the chip about 6 months ago and it is still pinking (although a bit less). It is now pinking noticably even under steady accelleration (dare I say, its getting worse).

About the car
I always top up with 98 RON where possible. The car never goes above oil temp of 94 when cruising but up to 108 in heavy traffic, at which point pinking is worse. It pulls just fine, no hesitation. K&N panel filter with drilled airbox, 4 branch stainless manifold (not heatwrapped) and powerflow stainless exhaust system. Head gasket done about 2 1/2 years ago. Uses 1 litre of oil every 1000 miles (valve stem seals) and a tiny bit of water.

A previous garage suggested the head could be coked up causing hot-spots and then pinking.

So...?
What is most likely?

Needs re-tuning?
Needs decoking? (I tried the pint of water through the vacuum pipe whilst running trick, seemed to help a little bit)
Poor fueling? (again it pulls ok and does 36-40mpg)

Help! 

[Horney]

Could be your knock sensor has packed up and it ca't adjust the timing.

Nick

[DarnPB]

As just said, it could be your knock sensor or your spark plugs could be worn, or wrong temp range fitted.

[Tristan 2.0 8v]

I concur! Change the knock sensor and all should be fine 

[dabill]

if you do change the knock sensor, make sure you buy a decent torque wrench, clean the thread out on the block where the sensor goes and make sure the contact surfaces are sparkling! this means that when you torque up the knock sensor(and its vital you torque it upto the right level) you wont get false readings cos of bit of what can only be described as sh*t that are in the threads and between contacts, causing a false reading, causing rubbish advance on the engine, causing pinking.

do it propperly first time and it will be fine after.

p.s. havent a clue what the torque setting is, look in the haynes...

[cняis]

thanks guys, i spent ages typing that up and FORGOT to mention that the knock sensor wiring looks VERY tired!

i will be buying a new sensor then... but where from... cheap enough from the stealers?

edit:

will this fit?
http://cgi.ebay.co.uk/Mk3-Polo-G40-Knock-Sensor_W0QQitemZ230228441285QQihZ013QQcategoryZ9889QQtcZphotoQQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[83coupe]

i need to do this aswell, whats it to be torqued up to?