My 1989 9000S n/a auto, has developed a problem. At 2000 to 2300 rpm whether accelerating or decelerating, on or off load, the engine pinks (pre-ignition, detonation call it what you will). I've checked plugs, distributor cap and rotor arm, all the vacuum hoses I could see, but the problem still persists.
Can anyone help?
Cheers
Richard