Supaglu

Hi, The ignition timing can be altered - by 5 deg's, but only with the "Select monitor" - the diagnostic equipment used by the subaru dealers. Regards Dave H.

Also thermostat may be worth checking - check top and bottom radiator hoses to see if they both feel the same temp when guage says warmed up. Dave H.

Hi, Have you thought of getting it onto a 4 gas emission analyser - if possible get two readings, one when cold and one when it's warmed up, I think you may be concentrating too much on the "too rich" idea, just because cylinders 1,2 & 4 plugs are black doesn't always mean that it's too rich - it could be that they are not firing efficiently enough so that they soot up - after all number 3 is ok !. If possible please post 4 gas readings here !. Regards Dave H.

I know an elderly gentleman who when returning his subaru for its first service asked - "how do you turn on the radio" ?

Hi, If you get this "noise" by revving the engine to 3,000rpm - then why not try this - get someone to rev the engine till you get the noise - disconnect each of the injectors in turn to see if the noise either goes away or gets a lot better - if it does then it will be somewhere in the bottom end - if not it may well be the flexplate as previously suggested. This will also tell you which cylinder the problem bearing, piston, big end etc is on.