Ok so heres how my day went.....

Swapped the injectors round and went for a spin, between 3-4k revs under heavy acceleration I experienced a seconds hesitation and MIL illuminates, continue to push it and it drops out and loses all power; read DTCs, P0303, swapped plugs around and went for a spin, same conditions met and MIL comes on, P0303, this time as I now know its not something i'd done wrong with the chain I left it running like a dog and scoped the injectors, sure enough the ECU had switched number 3 injector off; cycle the ignition and it returns to normal. As i've been running around a bit in it I now noticed a tapping noise from the top of the engine; using my top of the range stethoscope (screwdriver), this showed the noise to be originating from around the exhaust valves of cylinder 3. Given my results and the now known fact that these suffer from head/valve issues I decided to leave the electrical things alone and have another look at cylinder conditions.

I removed the oil filler cap with the engine running and a dominant hissing sound could be heard so I smoked the inlet at the throttle body. Despite no visual leaks, the leak indicator on the side of my smoke pro strongly suggested otherwise, I removed the filler cap again and instead of the expected wisp of smoke, I was greeted with a loud hiss of depressurisation and smoke bellowing out of the cam cover.

With a warm (neither hot nor cold) engine I repeated my compression test, although all healthy readings, cyl1-185psi, cyl2-215psi, cyl3-200, the 15% difference between cylinders 1 & 2 was suspicious especially as it wasn't on the mysterious cylinder 3!! I did a cylinder leakage test and number 2 proved to be excellent, number 1 was mediocre and cylinder 3 piss poor!

Having also tested the emissions to reveal very unstable readings at both idle and fast idle, with the exception of hydrocarbons which hovered between 500-600ppm, and also double checked the timing, still ok, I decided to call it a day and recommend stripping the engine for further investigation.

The customer is going to offer the owner his money back and put the vehicle through an auction as it runs spot on with no lights as long as its not driven hard!!!

Its been an interesting experience, and although some of the compression and cylinder leakage tests are the wrong way round I feel that a strip down is the most logical step forward, just a shame he doesn't want to go there, cant blame him though!

Thank you to everybody that helped me on this one it has been greatly appreciated!!

Craig

P.S. So much for the VW dealer and their timing chain diagnosis eh!?!