Poor running

Hello I bought a harness for a aftermarket Ecu and when I sent it for dyno tuning while on the dyno when the car is over 3k rpm it starts to run rough checked a lot of things and all seems to be ok however looked at the harness and the crank cable isn’t shielded and it’s a vr sensor do you think that is what is making it run rough?

There may be several possible things, or even a combination - the easiest way to know is to look at the signal trace when it's running close to, and above, that rpm. It should have a nice clear trace - it it's jiggly or full of hash, it'll need sorting out.

It should also show at any load, not just under load.

As Gord mentioned, misfiring can be caused by many things, and you can end up in a situation where a triggering issue is causing misfiring, or a misfiring issue is causing triggering errors.

If the crank cable isn't shielded, whether that's your root cause or not, I'd use a shielded cable. Any time you can resolve a potential cause of current or future issues, worst case it doesn't solve today's problem, but it avoids a future issue.

Thank you for the help I have ordered some shielded cable to replace it with

Sounds good, you're welcome. Beyond that, you may need to scope the triggering inputs then verify your trigger tooth detection settings make sense given the scope data you collect. It's possible actual voltage isn't high enough to have ample clearance above your arming voltage for tooth detection.

Trigger design, how well the trigger and sensor are mounted, can also be factors.

Then there's the ignition system side of things, your spark plugs, etc. depending on the setup. Keep narrowing things down and you'll get it sorted out.