Zafira missfires when 3250r/pm is reached?

Zafira 1.8 Elegance 2005 (+- 197000km). Skidcontrol light and engine goes on when revs reach about 3250r/pm. It starts to missfire. I switch the vehicle off for about 10 seconds and re-start the vehicle and the engine light stays on, but the car is driving fine as long as I stay below 3250r/pm. It can even happen at 3000r/pm, when the car is cold. Recently the engine needed to be rebored, because valve guides broke and ended up in the piston chambers. Since I recieved the vehicle after repairs, I have this new problem. I had it back to an Opel Dealer in Kuilsriver, Cape Town, South Africa, but they cannot find the solution to this problem.