Howdy
My mums magna is a 3l v6 ts with 240000ks on it, over time it has developed a problem only when cold ,when you accelerate off it misfires and carrys on all the way through the rev range like stuttering once it's warmed up it completely goes away any thoughts.
Plugs and leads have been replaced and throttle body cleaned

Also it only misfires under load it will idle fine

Have you check the distributor cap? Check the points, also check that there isn't any muck or liquids under the cap.

Could be a fueling issue of sorts, maybe try some injector cleaner, it might not do much but could help.

Yeah I tried the injector cleaner but I remember when my tp magna had a twisted fuel line running from the filter and that felt really bad compared to my mums car and it was constant ,I guess I'm gonna focus on the distributor there's probably a big crack in it or something obvious hopefully