Car runs fine unless accelerating on light throttle from 2500rpm then it kangaroo's untill 4000rpm then its fine. No codes ever seen with any scanner, software checked at dealer, who also has driven it and has no idea what is causing the fault.
Car is fine if driven a little harder, and has so far had fuel regulator & throttle body swapped from a 2nd car with no change.
Front O2 is a wide band sensor so cant see whats going on when fault happens re mixture.
Any ideas please?