SR20 Timing scatter / Incorrect timing

Have come across a issue thats left us a little stumped, car runs a nistune (SR20DET PFL S14) and well Nistune software displays 20 degrees even adjusting the cas its 20-30 degrees advanced past the last crank timing mark at idle.

Ive also installed a link into it for diagnoises purposes and with the timing locked at 20 degrees and setting offset to make it match as rpm increases the timing starts to advance more and more with higher rpm up to about 30-40 degrees past the last timing mark (20 deg) with the rpm I'm keen to get to with the timing advancing the way it is when it should be staying static at 20, Link isn't catching any trigger errors and link trigger scope stays consistent.

Has had cam chain and vct gear replaced as was noisey with new genuine nissan parts with no change to issue (wasnt expected too) and have also tried another cas. can a bad ignitor cause timing to scatter like this? I've never come across anything quite like this before.

Also have verified that the timing mark on the crank pulley is correct with its 0 deg placement at TDC.

Are you using an HT lead between the coil and sparkplug for the timing light? If using the "timing loop", that will cause large errors with many timing lights.

Does it run like its actually too far advanced? I have also seen the rubber bond on the front pulley/damper fail so the pulley slips around the hub on a couple of different nissans before.

It runs extremely poorly and erratic. I've tried two timing lights one being a basic old school one and one being a high end snap-on and tried from both the loop on coil loom and using a HT lead between the coil although I havent tried the HT lead since testing the Link only with the Nistune but all options gave the same result with the Nistune, I'll use a lead and lock it on the Link to double check.

Owner bought it running average and progressively got worse over the next day or two until it wouldn't really run or idle but would apparently start to clear up and go in higher rpm and it had a bad vct gear rattle.

I had the same thought about the pulley too and have verified the 0 deg mark matches with mechicial TDC, i'll spend some more time on it tomorrow and post how I get on.