Vauxhall Zafira keeps losing power wen driving

Every possibilty that it's the coil pack , very common .Also check plugs .Though that code is " P0420 Catalytic converter efficiency below threshold, possible causes Catalytic converter failed, wiring or O2 sensor 2 (post cat) faulty."

i have changed the 02 sensors both of them it happend a couple of month ago so i changed the coil pack but it feel like that if it not any ideas as the cat is in perfect workin its not broke

Cant figure out your post . You ask if it could be coil pack and on reply you now say coil pack replaced .Check wiring to coil pack also .

It happend about six month ago so i just put an old coil pack on from my old car an it feels like it was bk then its got 2 new 02 sensors on it the cat is only about 9 months old it looks perfect inside i can b driving for a gd hour the wen i am driving it will just start slowin down then starts juddering how i also put a new throttle body on it airflow mass then it was gd an how do i chek the coil pack wire

hi how do i check the coil pack wire there is no folt codes coming up the only one that did was the 02 censer they have both been replaced and there sound now any other ideas as its driving insane thanks