"the cam and crankshaft marks are in line."

This won't help with the NOx problem, but I've never heard of anything in the EZK system that would advance the timing. But harmonic balancers are known separate, which could make the timing look advanced to the timing light.

If the outer part of the pulley/balancer has slipped only about 1/4", the pulley "reference" notch would be at 20° BTC when the crank is actually at 12°. The more the pulley notch slips left/CCW (as viewed from the front), the "earlier" it would look to a timing light

I saved a pulley that slipped, and found the "0" notch was about 90° CCW from where it should be. My first clue was when starting a T-belt job, and looking thru the oil fill hole the first 2 cams were obviously wrong, as was the Cam sprocket mark—when the crank pulley notch was (supposedly) at "0".

You can get close to true 0 by feeling for the piston top thru the plug hole as you slowly come up in it. At 0° TDC Compression for #1, with both valves fully closed the #1 cam will be pointing inboard-upward about 30° and the # 2 cam will point outboard almost horizontally.

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Bruce Young
'93 940-NA (current), 240s (one V8), 140s, 122s, since '63.