Torsion value 2.0pd BMM worth adjusting?

Since having the cam belt changed a couple of years ago I've never been convinced that the engine runs as smoothly as before. I've just had the car scanned and the torsion value logs as -2.0, I understand that this should be as close to zero as possible. Just wondering if anyone who has any experience with these engines thinks it is worth tweaking or leaving alone?

Thanks,

Mark