Mg Zr Engine Issue

[BigRooster]

My son owns a mg zr 1.8 (vvc) he tells me his car is running normally untill it reaches 4k on the revs then there's a slight power loss then picks pack up again .
There no engine management light coming on so finding it hard to pin point the problem I hope some one here my have an answere.

[TWR]

There are a Number of things that could cause this problem Big, it needs to be diagnosed by a fault reader, " Not a Dealer" RE/Costs, ask any Garage that have the reader.